Sheryl Sandberg

Sandberg has been Zuckerberg's key business lieutenant since he wooed her from Google in 2008. She's now the company's chief operating officer. Her base salary is a modest $300,000, but that's helped by almost 1.9 million shares, which are now worth $72 million. Don't cry for Sheryl, however: The real money -- as in billionaire -- will come as her restricted stock vests.