According to eMarketer, U.S. mobile ad spending grew 180 percent in 2012 to $4.1 billion. This better-than-expected increase is “due in large part to the success of so-called ‘native’ ad formats like Facebook’s mobile newsfeed ads and Twitter’s Promoted Products,” according to eMarketer. Mobile ad spending in 2013 is expected to reach $7.2 billion, up 77.0 percent from this year’s figure. By 2016, mobile ad spending in the U.S. is expected to balloon to $20.9 billion. These projections reflect big upward revisions from eMarketer, which cites Facebook’s strong mobile performance in the third quarter as a major reason for the change in expectations. In 2012, Google claimed $2.2 billion of total net mobile ad revenues in the U.S., followed by Facebook with $339 million, Pandora with $225 million, Twitter with $135 million and Apple (iAd) with $124 million. According to eMarketer, Facebook is expected to rake in mobile ad revenues of $851 million next year, which would reflect a 151 percent year-over-year increase. (eMarketer)