• by Mark Walsh  @markfwal, August 12, 2010

Ad spending on Facebook will double to $1.28 billion worldwide in 2010, according to a new forecast by eMarketer. The bulk of that amount, or about $835 million, will come from the U.S.

By contrast, spending on rival social network MySpace will fall 14% to $297 million, reflecting its diminishing stature among marketers. The new estimate comes as MySpace gets set to roll out a revamped home page next week to help recapture user interest.

"Brand advertisers are making Facebook a core buy," said eMarketer senior analyst Debra Aho Williamson, in a statement. "Ad spending is building quickly and the mass audience is one that marketers cannot ignore any longer."

eMarketer cited Facebook's self-serve ad system as a key factor in the company's rapid ad growth, accounting for at least half of its revenue. The firm projects Facebook's ad revenue worldwide will hit $1.76 billion.