eMarketer has significantly upped its predictions for US mobile ad spend thanks to the success of “native” ad formats like Facebook’s mobile newsfeed ads and Twitter’s Promoted Products.

The company, which in September forecast 80% year-on-year growth in the US mobile ad market to $2.61bn, now predicts expects US mobile ad spending to reach $4bn this year, rising to $7.19bn in 2013 and nearly $21bn by 2016.

eMarketer said that it had changed its mind because of the success of the so-called “native” ad formats, which “represent a seamless experience across platforms for consumers”. This, in turn, means platform owners are able to earn revenue as consumers continue to increase time spent on mobile devices.

Facebook, which offered no mobile ad opportunities at all before 2012,  has had a significant role in this upturn, eMarketer said.  It now expects Facebook’s US mobile ad revenues to hit $339m in 2012.