Interpublic Group is in final negotiations with social networking site Facebook for a 0.5 percent stake in the site in return for spending up to $10 million for the agency's clients on Facebook, reports MediaWeek. The deal could be completed this week and would give IPG not only display ad opportunities but also access to Facebook user data (its 7.5 million users' profiles detail favorite bands, books and hobbies).

The IPG deal could also help Facebook develop an ad model beyond its current heavy reliance on third-party ad networks. "With this focus, we will be able to deliver more innovative advertising solutions to all marketers," Mike Murphy, VP of sales at Facebook, said in a statement.

The IPG investment implies a $2 billion valuation for Facebook (in April, it reportedly turned down a $750 million offer, seeking $2 billion instead). With 14 million visitors in May, according to ComScore, Facebook ranks seventh in terms of pageviews.