CEO and Chairman, The Washington Post Co.
For years, the CEO and chairman of The Washington Post has been a mentor to Zuckerberg. (Zuck reportedly spent a few days shadowing Graham to pick up some tips on being a CEO.) But the relationship isn't a one-way street: Facebook's chief executive has also helped Graham become savvier when it comes to online efforts. In fact, the back-and-forth contributed to the launch of Social Reader, the Facebook app that shows friends what users are reading. And although Graham hasn't been publicly tied to Facebook's IPO process, his seat on Facebook's board of directors likely gave him a good view of the proceedings.