You get a lot of video streams. Close to 10 million, says YouTube, adding that Sunday’s live Webcast of U2′s Rose Bowl concert was the single largest event it has streamed so far.

Granted, Google’s (GOOG) video site only started streaming live events last year, and doesn’t do them very often. But this was a pretty good muscle-flexing event, and by all accounts it went pretty well–I read some gripes about the site limiting transfer speeds, but many more raves about the quality of picture and sound.

That 10 million number, spread out over two-plus hours, doesn’t really tell us how many people watched the concert or how many did so concurrently. YouTube’s first attempt at live streaming, its weird “YouTube Live” concert/award show, may have attracted a peak audience of 700,000.

For some context, consider that last week’s episode of “The Mentalist” on CBS (CBS) drew 11.8 million viewers, which made it the 20th-ranked show in the U.S. But the fact that YouTube is even playing in the same league gives you a sense of the site’s reach.

And recall that YouTube boasted this month that it is now streaming more than one billion streams per day, which means that the overwhelming majority of its users were watching something other than Bono and company on Sunday.

You can see an amazingly high-quality version of the concert here, though it isn’t embeddable. But here’s a clip of a fake U2 concert from a couple of years ago.

Here’s a video I did while attending YouTube Live on Saturday–well, live–at the Herbst Pavilion at the Fort Mason Center, right on the San Francisco Bay.

The last time I had attended a big tech industry event here, it was the launch of Windows 97 from Microsoft (MSFT)–which was quite a different scene than this entertaining but freaky show, in which online celebrities jumped a little shakily into the analog world.

Let me just say, online celebrities make real-world ones seem 1,000 percent more interesting. But there is also a homespun sweetness to them too and a look-at-me striving that can be downright heartbreaking.

YouTube Live was the online video giant’s “first ever official live community celebration” and also its first try at a live-streamed event. The YouTube Live broadcast online drew about 700,000 viewers at its peak.

As such, as Peter Kafka of MediaMemo notes: “That is almost certainly a record for a Web-only event. But it’s a nonevent by mainstream entertainment standards.”

I am not sure big ratings were the point, though. Nonetheless, the show did attract a passel of Internet stars, including YouTube Founder Chad Hurley, who sat with Google Co-Founders Larry Page and Sergey Brin right up front. Google (GOOG) owns YouTube.

Here is a video of the event, including an interview I did with Obama Girl, as well as Hurley, and also some snippets of the professional performers (Katy Perry, Will.I.Am and Akon) and a passel of online celebs (including the “Free Hugs” and “Will It Blend” guys) appearing onstage:

Please see this disclosure related to me and YouTube (which is owned by Google).

That is almost certainly a record for a Web-only event. But it’s a nonevent by mainstream entertainment standards.

A poorly performing show on network TV, by comparison, draws millions of viewers: Recall that GE’s (GE) NBC canceled “Quarterlife,” the soap opera that started out on MySpace, after it drew an audience of 3.1 million in its debut. A bona fide hit draws many millions more: Last Thursday’s episode of “CSI,” for instance, garnered more than 18 million eyeballs.

Not fair to compare a weeknight audience to one on Saturday nights? OK. Try this: Last year, before anyone had ever heard of Sarah Palin, “Saturday Night Live” was averaging more than five million viewers.

You can’t blame the modest audience on a lack of effort on YouTube’s part. The video site generated plenty of publicity in advance of the event. And heavy promotion on the site itself all but compelled visitors who ventured onto YouTube last night to check it out.

Part of the issue, I think, is that while the show had a smattering of sort-of-popular singers (Katy Perry, Akon) there was no one really huge. Most of the show was dedicated to viral video stars/oddities like Tay Zonday. And the point of viral videos is that you see them on your own time, serendipitously: You take a couple minutes out of work on a Tuesday afternoon to watch Tay Zonday sing “Chocolate Rain” because your friend sends you the link. Not because he’s appearing live on Saturday night.

Could YouTube rustle up a bigger audience for a live event in the future? Absolutely. It’s one of the biggest Web sites in the world, so if it had a truly compelling show, instead of a niche event, it wouldn’t be hard to get the word out. And if parent company Google (GOOG) wanted to lend a promotional hand, game over.

So maybe that’s coming down the pike. In the meantime, if you didn’t tune in last night, here’s a sample of what you missed: Katy Perry singing “Hot ‘N Cold.”

This weekend, YouTube is going analog, showing off a bunch of the freaky people who have become online phenoms, at YouTube Live, its “first ever official live community celebration.”

Taking place in San Francisco on Saturday, BoomTown and thousands more are going.

And, frankly, I am not sure I want to meet some of these folks, including the truly warped Fred Figglehorn (the No. 1 most subscribed channel in YouTube history), Obama Girl and Brandon Hardesty, the guy who does movie reenactments.

Also attending the event by YouTube, which is owned by Google (GOOG), are some actual stars, such as singers Akon and Will.I.Am.

YouTube says there will be more than 50 YouTube and real-world stars scheduled to appear, with a combined 2.5 billion video views on YouTube.

Will I be bringing my video camera? In the words of a more recent YouTube phenom, Governor Sarah Palin: You betcha!

Here are some YouTube phenoms:

Obama Girl

Fred Figglehorn

Brandon Hardesty

Will.I.Am

Please see this disclosure related to me and YouTube (which is owned by Google).