Research firm eMarketer boosted its September forecast of 80 percent growth in mobile advertising spending in the U.S. for full-year 2012 all the way up to 180 percent, largely due to initiatives by Facebook, including its incorporation of ads into the mobile news feed.

eMarketer said it expects U.S. mobile ad spending to reach $7.19 billion next year and nearly $21 billion by 2016, saying of efforts by the social network and its counterpart, Twitter:

U.S. mobile ad spending is growing more quickly than previously expected, due in large part to the success of so-called “native” ad formats like Facebook’s mobile news feed ads and Twitter’s promoted products. These products represent a seamless experience across platforms for consumers, which means platform owners are able to successfully earn (or, in some cases, not lose) revenue as consumers continue to increase time spent on mobile devices with smaller screens unsuited to much of the inventory that accounts for the bulk desktop display advertising.

Facebook’s third-quarter mobile performance is one major reason for the change. The social networking giant offered no mobile ad opportunities at the beginning of 2012, but grew its mobile business at an astonishing — and unexpected — rate. Before Facebook’s Q3 earnings call, most researchers and analysts expected U.S. mobile ad revenues of roughly $45 million to $100 million, according to figures examined by eMarketer. While the company’s total ad revenues were, for the most part, unsurprising, the share of revenues attributed to mobile advertising was far from it.

eMarketer — which bases its figures on a meta-analysis of data from research firms, investment banks and other sources on ad revenues, ad impressions, ad pricing, and other factors — now estimates that Facebook’s U.S. mobile ad revenues will hit $339 million in 2012.

The research firm added that it now expects Facebook to claim an 18.4 percent share of the U.S. mobile advertising display market for full-year 2012.

Readers: Are you surprised with the quick progress Facebook has made on the mobile advertising front?

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