Facebook is so large that it now accounts for about one out of every three ad impressions in the U.S., according to the latest statistics from comScore Ad Metrix. In the first quarter of 2011, comScore estimates that 1.1 trillion ads were served to U.S. Internet users, and 346 billion of those (or 31 percent) were on Facebook. This percentage is up from 23 percent in the third quarter of last year.
No other Web property even comes close to Facebook in terms of number of display ads served. Yahoo is No. 2 (with 10 percent share), followed by Microsoft (5 percent), AOL (3 percent), and Google (2.5 percent). These figures are just for their own sites, and do not include their ad networks.
Facebook has the volume, but it is also beginning to experiment with new forms of ads which are themselves more social. These ads look more like News items shared by friends than typical display ads. Until those start kicking in, however, Facebook can just keep putting display ads on its ever-growing share of pages people look at on the Internet.