14. Shana Fisher, Senior Vice President for Strategy and M&A, IAC/InterActiveCorp
IAC/InterActiveCorp chairman and CEO Barry Diller loves his online enterprises. IAC has purchased Ask.com, Expedia, and a host of other Web businesses. But who tells Diller where to plunk down the cash? His mergers and acquisitions advisor, senior VP Shana Fisher, determines exactly where and when IAC should invest. Her control over IAC's purse strings makes her arguably the most powerful woman on the Internet.