A lot of big interesting names hit the big 4-0 in the past year, and so they didn't make our cutoff for the main list. They still deserve a mention.
Facebook's No. 2 executive is working to make the site as lucrative as it is popular. Just last month, Facebook hit 300 million members -- up from 100 million a year before.
Sandberg, who built the highly profitable AdWords business at Google, was recruited in early 2008 to help Facebook profit from that rapid growth.
Critics can point to the social networking site's stumbles in courting advertisers. But Sandberg expects to make all that personal user data pay off for Facebook--sooner rather than later.
NEXT: Austan Goolsbee