A big endorsement today for mobile advertising from eMarketer: their analysts today said they were revising up their forecasts for U.S. mobile ad spend to $2.61 billion, from their previous estimates of $1.8 billion. Why the rise? Google’s “exceptional” mobile advertising performance in mobile search advertising, and more reliable market data.

 eMarketer were the same analyst house that last year revised up their mobile ad forecasts to over $1 billion—the first time a company had made that proclamation. In the event, those revenues reached $1.45 billion, they said, nearly double what they were in 2010. Their 2012 figure represents a rise of 80 percent on last year.

Yesterday Yahoo’s new CEO Scott Thompson claimed that there wasn’t yet a clear leader in mobile advertising, and that it was still an open field. That may be the case in that there is still a lot of room for growth, but there is actually a company dominating the mobile ad business at the moment: Google (NSDQ: GOOG).

In 2011 eMarketer says that Google had about 51.7 percent of all mobile ad revenues, with sales of $750 million. The second-two biggest platforms were far behind it. Apple’s iAd took in $92.4 million for a 6.4 percent share; while Millennial earned $90.9 million for a 6.3 percent stake.

Google totally dominated the mobile search category—an area where Apple (NSDQ: AAPL) and Millennial currently do not play—with some 95 percent of all revenues. Google was not shabby in display, either, leading in that category, too—although not as comprehensively, with only 24.8 percent of the market, with Millennial Media and Apple’s iAd very close to each other for second place.

As a sign of how fragmented mobile display advertising remains, “other” was the biggest category of all with 39.6 percent of all sales.