Most of that revenue will come from advertising, Ryan estimated in an interview with Reuters this week.

The $1 billion forecast also includes revenue from Facebook Credits, which allow users to buy items for games and other activities on the social network, he added.

Ryan is now chief executive of luxury flash-sales company Gilt Groupe, but he invests in other Internet businesses including news website The Business Insider and 10gen, which runs MongoDB, a database that's popular with start-ups.

Facebook's more than 500 million active users are attracting a lot more ad dollars as companies step up online marketing. Research firm eMarketer estimated in January that ad spending on Facebook would exceed $4 billion this year. That's more than double levels of 2010.

A big chunk of that ad revenue comes from social games that are played on Facebook's platform. "Assuming Facebook is on track to produce $4 billion in ad revenue this year, $1 billion of that coming from social gaming is not outlandish," said Paul Verna, a senior analyst at eMarketer.

Facebook is a private company and doesn't disclose financial information. A Facebook spokesman declined to comment on Friday. Zynga Inc, the dominant developer of social games played on Facebook, filed for a $1 billion initial public offering on Friday.