The Facebook CEO did say there is “almost a guarantee” that the company will double its user base from 500 million to one billion, which is pretty heady stuff, but also pretty hazy stuff. (We already know that Facebook is really big.)

And Zuckerberg again danced around the question of Facebook’s eventual IPO. But unless he flat-out declares that the company will never go public, there’s almost no reason to ask him about it: Facebook is quite clearly headed for an IPO, one day.

Zuckerberg’s summation of Facebook’s global hegemony is worth pondering for a minute, though:

Facebook’s global domination is almost complete, he said. “We are down to just four countries where we aren’t the leading social network.”

Zuckerberg added that in Russia Facebook had just 1 million users, the kind of numbers that saw AOL sell off Bebo and ITV relinquish Friends Reunited. But in Facebook’s case, growth is “doubling every six months”, according to Zuckerberg, and Japan and Korea have similar user bases.

He said that Facebook can tell when an explosive growth “tipping point” is about to be reached by who is “friending” who. When Facebook first launches in a country, nearly all the friend connections are with foreign Facebook users.

“We know that a country has tipped when local-to-local connections outnumber local to foreign,” he added. “It is a long-term thing [and with regard to the four left to tip] we are probably not going to win in six months, not in a year [but] things look promising in three to five years out.”

Meanwhile, if you want a really deep dive with Zuckerberg, check out Inside Facebook’s recent Q&A.

Sources tell me that the mobile social network, which lets you tell your friends where you are, is lining up a new round of financing to bolster the $1.35 million it raised last August. CEO Dennis Crowley declined to comment.

I don’t know how much the year-old company intends to raise or the valuation it’s looking for. But speculating about both is a fun pastime for venture capitalists, who agree on one thing: The company won’t have any problem attracting suitors.

“Everybody and their mother is humping their leg,” says a VC who readily admits to Foursquare infatuation. So many investors are besotted that the chatter can get feverish. Another VC passes along a rumor that an investor offered to buy into the company at a $100 million valuation.

A more reasonable guess: New York-based Foursquare will wind up bringing in a West Coast-based VC, who will lead a round in the $10 million range that will value the company at something like $40 million. Foursquare’s first round valued the company at more than $6 million.

So what’s the appeal? Like plenty of other social media start-ups, Foursquare has minimal revenue. But it has a great story, which contains plenty of allusions to Twitter.

Like Twitter, Foursquare was founded by an entrepreneur who already built a start-up and sold it to Google (GOOG). And like Twitter, Foursquare launched at South by Southwest to some fanfare, and has seen its user base increase at breathtaking velocity.

When Crowley raised his first round of financing from O’Reilly AlphaTech Ventures and Union Square Ventures in August, Foursquare had some 50,000 users. That total is now approaching 600,000, boosted by a burst of 100,000 sign-ups over the last 10 days.

And while Foursquare, like Twitter, doesn’t have real revenue to speak of, it does have a notion of how to get some. It is working on tie-ups with local merchants, who can reward users who “check in” at restaurants, bars, etc.–and by doing so, provide free advertising for those establishments.

Foursquare still doesn’t do anything for me, but the service is doing just fine without buy-in from a middle-aged dude who doesn’t go out at night. And because Foursquare is a fun, buzzy story to write about, it gets written about a lot.

The real question for Foursquare: How will the start-up keep Twitter and Facebook from rolling over it? Twitter added its location feature this month, and Facebook is reportedly adding its own in April.

Both these companies have plenty on their plate, so it’s possible they won’t spend much effort chasing Foursquare’s niche. Still, it’s hard to see room for three social networks that let you broadcast your whereabouts to your pals. But that’s not dissuading guys who can write big checks.

The most recent example: A new wave of phishing attacks, which are generally–but not always–sent via the service’s “direct message” feature. And which generally–but not always–feature language like “LOL is this you” in the message.

Like most phishing attacks, this one has some telltale signs, if you’re the kind of person who’s inclined to see them. There’s the odd text in the message itself. And the “bzpharma” text that appears in the URL address is a big giveaway.

But! As with many other phishing attacks, if you’re not looking for this stuff or you’re just clicking quickly, it’s easy enough to get duped. The fake Twitter homepage created by the phishers looks real enough, as does the “fail whale” message you get after entering your info.

One easy step you can take to arm yourself against this kind of thing: Follow Twitter’s “Spam Watch” account, which does a decent job of keeping people informed attacks like these. But while that account has 148,368 followers, and tends to get retweeted a lot, the majority of Twitter users still won’t learn about this stuff in advance. Maybe it’s time for Twitter to build some equivalent of the emergency broadcast system.

Meanwhile, if you don’t like reading, the video below from the Sophos security firm (via Mashable) gives you a good idea of what this is all about.

But Spotify has yet to make a key expansion: To the U.S., where the big music labels worry that consumers will love everything about the site except paying for it. That’s bad, since Spotify is supposed to work best as a subscription service.

Most Americans have never heard of Symbian, though it remains the biggest player in the global smartphone market (as long as you use a broad definition of smartphone). But it’s telling that Spotify made a point of making its service compatible with Apple’s (AAPL) iPhone and Google’s (GOOG) Android handsets first.

In any event, Spotify is only available via mobile to paying subscribers, who shell out around $16 a month in the U.K. (and less in some countries). They key question for the music business is how many subscribers there are.

Spotify won’t release statistics, but one number that I’ve heard from people close to the company is 100,000, which works out to less than two percent of the company’s overall user base (free users can listen to the service only on their PCs and have to endure a small smattering of ads). But U.S. music industry executives worry that the subscription number may be even lower than that.

The two sides continue to chat, and conventional wisdom is that the service will indeed get to the U.S. one day. But at one point, Spotify was talking about coming to America in 2009, but that looks just about impossible. Now, CEO Daniel Ek is talking about the first half of 2010.

What else would you expect Ballmer to say? Now that Microsoft (MSFT) has got its hands on Yahoo’s (YHOO) search business–without paying a “boatload” for it–there isn’t a whole lot left to buy.

Emphasis on the word “buy.” Microsoft may still be willing to write a big check to boost its search share, specifically to get its hands on queries controlled by Time Warner’s (TWX) AOL, which has about three percent of the domestic search market.

AOL currently outsources its queries to Google (GOOG) in a deal that is said to make quite a bit of money for both sides of the table because AOL’s core user base tends to click through at a much higher rate than the rest of the Web. But AOL’s Google contract is expiring, and both Mountain View and Redmond are thought to be in hot pursuit of a new one. AOL CEO Tim Armstrong, though, is taking his time about his decision.

Also in the potential mix for Microsoft: A deal with News Corp. (NWS), which owns this site. Google’s $900 million search deal with News Corp.’s MySpace and IGN sites expires next year, but unlike the AOL deal, it has been a disappointment for Google.

It’s hard to imagine Ballmer spending much to wrest that one away, but News Corp. digital boss Jon Miller is doing what he can to drum up interest: He’s been talking up the idea of bundling multiple News Corp. properties–like, say, Dow Jones–into a larger deal. But since many of those properties have their own particular agreements and peculiarities, that’s going to take some doing.

The perennial, and obvious, solution is to incorporate ads into the service, but so far Twitter hasn’t tried it, except for very limited experiments.

The good news for Twitter and its investors is that the service’s user base is pretty receptive to advertising, in general terms, because it’s pretty receptive to just about everything on the Web.

So says research group Interpret LLC, which has a new study out today, conveniently enough. From the release:

Twitter users are twice as likely to review or rate products online (24% vs. 12%), visit company profiles (20% vs. 11%) and click on advertisements or sponsors (20% vs.9%) as those who only belong to traditional social networking websites like Facebook and MySpace. The data suggests that Twitter users uniquely demonstrate higher engagement with brands, not just with “tweets” they post.

These statistics are self-reported, and Interpret doesn’t say how big a sample its survey used, so take them with as much salt as you like. But they seem intuitively and directionally correct: Anyone willing to plug into the waves of information that Twitter pumps out is likely engaged all over the Web.

Note what the Interpret report doesn’t say: That Twitter users are eager to have ads inserted into the service itself.

Doesn’t matter. At some point, they’re unlikely to have a choice about that because it seems hard to imagine that Twitter can ever deliver on its investors’ sky-high expectations without generating some kind of money, somehow, from Madison avenue.

Which is exactly why Biz Stone and crew, who once made a point of expressing their derision for ads, now make a point of saying that ads may not be such a terrible thing, after all.

“As of today, Facebook now serves 300 million people across the world,” founder and CEO Mark Zuckerberg said in one of his typically somnolent blog posts. “It’s a large number, but the way we think about this is that we’re just getting started on our goal of connecting everyone. We’re also succeeding at building Facebook in a sustainable way. Earlier this year, we said we expected to be cash flow positive sometime in 2010, and I’m pleased to share that we achieved this milestone last quarter. This is important to us because it sets Facebook up to be a strong independent service for the long term.”

This is important to us because it sets Facebook up to be a strong independent service for the long term.

Interesting remark. It would seem then that Facebook has no interest whatsoever in selling itself off to Google (GOOG) or anyone else. It would much rather go public.

UPDATE: A couple of quick points courtesy Facebook COO Sheryl Sandberg: Growth is apparently widespread, and while it’s true that 70 percent of Facebook’s user base is now outside the U.S., growth in the U.S. is not slowing.

[Image credit: San Francisco skyline by m.john16/Flickr]

“As of today, Facebook now serves 300 million people across the world,” founder and CEO Mark Zuckerberg said in one of his typically somnolent blog posts. “It’s a large number, but the way we think about this is that we’re just getting started on our goal of connecting everyone. We’re also succeeding at building Facebook in a sustainable way. Earlier this year, we said we expected to be cash flow positive sometime in 2010, and I’m pleased to share that we achieved this milestone last quarter. This is important to us because it sets Facebook up to be a strong independent service for the long term.”

This is important to us because it sets Facebook up to be a strong independent service for the long term.

Interesting remark. It would seem then that Facebook has no interest whatsoever in selling itself off to Google (GOOG) or anyone else. It would much rather go public.

UPDATE: A couple of quick points courtesy Facebook COO Sheryl Sandberg: Growth is apparently widespread, and while it’s true that 70 percent of Facebook’s user base is now outside the U.S., growth in the U.S. is not slowing.

[Image credit: San Francisco skyline by m.john16/Flickr]

“In 2004, as you may recall, we launched a slim version of PlayStation 2, a defining moment for that console, helping us to really expand the user base of PlayStation 2 further,” Sony Computer Entertainment Chief Executive Kazuo Hirai said at the Gamescom videogame trade show in Cologne, Germany. “Today is that day for PlayStation 3.”

And so, starting Sept. 1, the PS3 will be available for $299. That’s still well above Microsoft’s (MSFT) Xbox 360, which retails for less than $200 and Nintendo’s Wii, which sells for $250, but it’s a hell of a lot better than $399. And analysts say it will almost certainly spur demand for the console. “People were expecting this to happen. [Sony] had to do something,” MKM Partners analyst Eric Handler told MarketWatch. “This will bring some new customers to the fold.”

Indeed. But how long can Sony sustain such market share gains, when Microsoft and Nintendo are almost certainly mulling price cuts for their platforms as well?

Instead, the New York-based company has just raised a $4.5 million Series B round that its CEO, 22-year-old David Karp, says will fund it for two and a half years. Union Square Ventures and Spark Capital, which led the company’s first $750,000 round a year ago, also led this financing. My educated guess is that its investors now value Tumblr at around $15 million.

Tumblr is a “microblog” platform that is supposed to let its users quickly create nice-looking posts with a minimum of effort; it sits somewhere between Twitter and full-fledged blogs like Blogger and TypePad. It is popular with a relatively small but prolific user base: Its 500,000 users have created pages that draw 15 million unique visitors and 61 million page views a month, Karp says.

Money? Nope. Tumblr is free–and has no ads cluttering up its hipster vibe.

Way back in 2007, those kinds of numbers would have been catnip for the likes of Google (GOOG) or Yahoo (YHOO). Now, though, even deep-pocketed buyers aren’t racing to snap up revenue-free start-ups. But Karp says raising money from his previous investors was easy: “These guys came to us with a deal that made us incredibly comfortable.”

Karp says he’s going to start generating money in early 2009. Not by selling ads on his members pages–Karp thinks the site will eventually incorporate ads in some way, but not yet–but by selling users “premium” services, most of which he’s not ready to describe. He does promise they will be “really sexy.”

More practically, Karp points out that other Web services, like the WordPress blogging platform and Yahoo’s Flickr photo service, have been able to upsell many of their users with goodies like extra storage. He figures many of his users will pay up, too.

The new money means he’ll have time to prove his thesis. Karp has just doubled his staff–which means there are now all of six people on payroll. One of them, hired in September, is John Maloney, Karp’s former boss at Urban Baby, where he started his Web career. Maloney is now in charge of business operations.

The money also means there are heightened expectations. Karp has done much more than people twice his age (and has the press clips to prove it). But the newest funding round means his investors think the company will be worth as much as $50 million by the time he sells it or raises more cash. In order to prove them right, he’s got a lot of work ahead of him.

[Image Credit: David's Log]