Google (GOOG) will end up paying $133 million for New York-based On2, a 20 percent bump above the price it announced it was paying way back in August. But a group of dissidents complained loudly enough and for long enough, apparently, to convince the search giant to pony up just a bit more.

When it did raise its price, Google announced that this was its last and final offer, which apparently convinced recalcitrant shareholders, who approved the deal today.

The deal brings Google’s acquisition tally to seven since August. That tally would have been eight had the folks at Yelp not turned down a $550 million offer in favor an injection of private equity money. But we’re almost certain to see more deals in this M&A spree.

UPDATE: Make that eight-plus. Google has “acqhired” Gabor Cselle, who founded email start-up reMail in 2008 and graduated from the Y Combinator hatchery in 2009. Cselle says Google will shut down reMail and remove the company’s app from Apple’s (AAPL) iTunes store.

That’s a 20 percent premium over the price Google originally announced it was paying for On2 in August, and Google (GOOG) says that’s the best it can do. On2 shareholders will get 15 cents in cash for every share in addition to the 60 cents worth of Google Class A stock offered in the original deal.

Will this appease On2′s dissident investors, who think the company is worth closer to $6 a share? We’ll know by Feb. 17, when the deal goes to a vote.

Google, of course, could easily pay much more to get the angry On2 contingent to shut up. And at this point, you have to wonder if the headaches associated with the deal are worth it–Google, remember, is valued at $192 billion.

But Google is in the midst of a lengthy shopping spree. And it certainly doesn’t want to revisit the price of every purchase it makes. Presumably, that’s why the company is playing hardball, or close to it, on this one.

That’s because Google’s plans to buy video compression outfit On2 have been held up by disgruntled shareholders. And the company’s plans to spend $750 million on AdMob, the mobile ad start-up, can’t go through until federal regulators sign off.

That may take a little longer than Google (GOOG) would like. The company announced today that the Federal Trade Commission has asked for more information–formally, a “second request”–as part of its review. From a post on Google’s Public Policy Blog:

…we know that closer scrutiny has been one consequence of Google’s success, and we’ve been talking to the U.S. Federal Trade Commission over the past few weeks. This week we received what’s called a “second request,” which means that the FTC is asking for more information so that they can continue to review the deal.

While this means we won’t be closing right away, we’re confident that the FTC will conclude that the rapidly growing mobile advertising space will remain highly competitive after this deal closes. And we’ll be working closely and cooperatively with them as they continue their review.

Google was well aware that it was going to face regulatory scrutiny on this deal; in fact, CEO Eric Schmidt says the company assumes regulators will now look at every big deal it makes, simply because it’s Google.

And also because Google’s competitors are doing their best to make sure there is regulatory scrutiny. Microsoft (MSFT), which knows a thing or two about regulatory headaches, helped slow down Google’s $3.1 billion purchase of DoubleClick for a very long time. And it’s quite clear that Redmond intends to holler loudly in Washington about other deals. Googlers tell me they also believe AT&T (T) agitates against them.

I’ve tried getting Googlers to guess at how long they think the AdMob deal will take to clear, but they’ve been pretty reluctant to do so. “I thought DoubleClick would take a few months, and it took more than a year,” one would-be bettor told me recently. “I’m not making that mistake again.”

Google’s (GOOG) bid represents a 57 percent premium over On2′s share price before the deal was announced on Aug. 5, but these shareholders claim the company and its video compression IP are worth more and argue that its board should have held out for a more lucrative offer. As one said during an August On2 earnings call, “We have the world class technology and we just sold it for just sixty cents.”

While it’s true that On2′s stock once traded as high as $3.99–back in 2007–that hasn’t been the case lately. And much as the company’s dissident shareholders would like to believe that Google’s demand of exclusivity in the negotiations and “no shop” provisions in the merger agreement prevented On2 from receiving competing buyout offers, that doesn’t seem to the case either. As On2 noted in a merger FAQ issued today, no other companies have inquired about a potential acquisition since the Google deal was announced. From that document:

Did the mid-cap sized publicly traded company in the semiconductor industry referenced in the proxy/prospectus that contacted On2 in late June 2009 express any interest in a transaction with On2 after the merger transaction with Google was announced?

No. On2 did, however, receive an email from such company following the announcement of the Google transaction in which company stated the following: “Congratulations on the transaction. Nice premium to market.”

Well, there you go.

Perhaps, then, On2 is not worth more than what Google proposes to pay for it. Obviously that’s the opinion of the company’s Board of Directors, which is literally begging shareholders to vote in favor of the merger. Said the board: “If the proposed merger with Google is not consummated, On2 may be forced to revert to a business model and strategy that are uncertain given On2’s size and limited resources and for which there can be no assurance On2 will ever achieve or sustain profitability.”

Yesterday, Yahoo CEO Carol Bartz said she was in the market for acquisitions–specifically “small and medium-sized opportunities.” Today, Google CEO Eric Schmidt said he’d use his $11 billion cash hoard to do the same thing. At the G20 gathering in Pittsburgh, Schmidt told reporters that now that “it’s clear that the worst is behind us,” his checkbook is open again. Reuters:

“Acquisitions are turned on again at Google and we are doing our normal maneuvers, which is small companies. My estimate would be one-a-month acquisitions and these are largely in lieu of hiring,” Schmidt said.

“There may be larger acquisitions, but they really are unpredictable,” Schmidt added.

And sure enough, Google has been on a mini-buying binge as of late. Last month, it was video compression company On2 for $106 million (though angry owners of the penny stock insist it should be for much more). Earlier this month, it was reCaptcha, the, um, captcha company, for an undisclosed sum. One decent bet for the future: Ad technology companies like Teracent.

Pretty sure I haven’t embedded any Bob Fosse clips before. Time to change that.

A stock-for-stock transaction, the deal will see each share of On2 exchanged for 60 cents worth of Google class A common stock. On2 shares closed at 38 cents Tuesday, so the company and its investors are presumably quite pleased with the deal.

As is Google (GOOG), which plans to use On2’s (ONT) advanced compression technologies to enhance YouTube and perhaps even make its own video infrastructure play.

“Today video is an essential part of the Web experience, and we believe high-quality video compression technology should be a part of the Web platform,” said Sundar Pichai, vice president, Product Management, Google. “We are committed to innovation in video quality on the web, and we believe that On2′s team and technology will help us further that goal.”