Facebook took an estimated $1.86bn in advertising revenue in 2010

"Facebook has long been a buzzword in discussions of new business models and the growth of new media, but in the wake of news that it is to float the business model it is coming under greater analysis. Some new advertising figures and user analysis provides more food for thought.
The social network now has more than 650 million global users and, according to eMarketer, it took $1.86 billion in advertising during 2010. That's an increase of 151% on 2009's figure of $740m. Most of the 2010 total, some $1.21bn, was earned within the US, which probably comes as no surprise.
What's more of a surprise is that 60% of 2010's ad revenue, some $1.12bn, came from smaller companies which used self-serve tools rather than dealing through media agencies. Major marketers such as Coke, Proctor & Gamble and Match.com generated $740m for Facebook."

Source:  Estimates from eMarketer, reported by Daily Finance, 24th January 2011