US advertising on social networks surges 20% to $1.68 billion, half of it on Facebook

Just after Facebook hit 500 million users last month, some analysts increased their 2010 forecasts for spending on social media advertising. US advertising is expected to increase 20% over last year to $1.68 billion, up from December's forecast of $1.3 billion, according to a study by digital research group EMarketer.

"That's primarily due to the strong performance of Facebook and somewhat due to the fact that we started adding Twitter to our analysis," said Debra Aho Williamson, an analyst. The study, conducted every six months, also measures sites such as MySpace, LinkedIn and Classmates.com as well as popular sites in China, Japan and Russia for worldwide figures. Half of that $1.68 billion spent by U.S. advertisers will go to Facebook, according to the study. By 2011, advertisers will spend $1.06 billion on the San Francisco company -- a 112% increase from 2009.