Marissa Mayer, 39
No one ever said turning around Yahoo would be easy, Mayer is facing restless investors as ad revenue remains challenged—and in the wake of the sale of part of the company’s stake in Chinese e-commerce giant Alibaba. The sale earned $9.4 billion for Yahoo—a portion of which Mayer may use to add to the some 40 acquisitions she’s made in the past two years. But investors are questioning her ability to create value with that strategy: the company’s core business is now valued at less than its stakes in Alibaba and Yahoo Japan. Two bright spots: Mayer has turned Yahoo into a player in content with big name hires like Katie Couric. And search-related revenue is up 2% year over year.