Facebook may be the brainchild of a 23-year-old whiz kid, but the future of the social network may rest in the hands of Sheryl Sandberg, a 38-year-old former Google executive who will serve as COO.

Sandberg, who previously ran global online sales and operations for Google, inherits a social network that is currently beset by growing pains.

Last month, Facebook faced down a small user rebellion over a program that allows members to delete their accounts. The social network also got mixed reviews with respect to its traffic. While time spent on Facebook increased, total traffic to the site actually dropped, suggesting to some that the social network is no longer worthy of the hype that surrounded it this summer.

Facebook also bid farewell to Owen Van Natta, the CRO who helped the company attract a $240 million investment from Microsoft. Days after Van Natta announced his departure, CEO Mark Zuckerberg said he was looking for an executive who could serve as a kind of second in command at Facebook. By all accounts, Sandberg appears to be that choice.

Whether Sandberg, who joined Google when it had fewer than 300 employees, can help Facebook exchange its startup label for one with more cache will come down to her ability to develop an ad model for the site. Beacon, Facebook's ill-fated ad program, went down in flames last year after a user revolt. Since then, Facebook hasn't been able to answer the monetization question.