Michelle Zatlyn

Cloudflare tangles with some of the nastiest people on the web, defending its massive customer base from cyber-bad guys of all stripes. So it's no surprise that Zatlyn credits grit as her most critical personal quality: helping propel her from a small town in Saskatchewan, Canada, to Harvard Business School, and on to build one of the most important security firms in the Valley (rumored to be heading toward an IPO). Zatlyn also has an idealistic streak, particularly when it comes to the open Internet, which she calls "the greatest invention in the last 30 years."