President, YahooRank: 7Why she matters: If Yahoo is ever to regain the upper hand in its rivalry with Google, Decker will be the one who makes it happen. After a long stint as Yahoo's CFO, Decker was tapped in December to take a new job as head of the company's advertising and publishing division, which generates most of its revenue, and in June as the company's president.
In the new role, her not-small task is to reposition Yahoo by tweaking its Panama ad system to deliver more customers to advertisers and more profit to publishers. Amid growing nervousness about Google's dominance, Decker has a real opportunity to succeed. If she does, she's a shoo-in to follow Terry Semel as Yahoo's next CEO.
Meet 50 Who Matter winner Gina Bianchini. Her site, Ning, lets anyone be a social networking mogul. (more) 
