Very interesting piece looking at the number of CEOs rising to the top via a Chief of Staff role. Lots of examples of senior leaders - Sheryl Sandberg being the highest profile (albeit COO rather than CEO at Facebook).
Just consider: Sheryl Sandberg, chief operating officer at Facebook, was Larry Summers' CoS when he was U.S. Treasury Secretary. Aileen Lee, now head of Cowboy Ventures, a VC firm in Palo Alto, California, filled the same position for Mickey Drexler when he ran The Gap. And Aretae Wyler, former CoS to Atlantic Media founder David Bradley, is now general counsel and chief administrative officer of the company.