In the public eye, security and data-mining company Palantir is a branch of the surveillance state, giving the FBI and CIA an inside line on our private lives. To CEO and co-founder Alex Karp, though, it's a tool that keeps users accountable while still helping catch terrorists and pedophiles — and a passion that now consumes most of his life. Brought on board by investor and longtime libertarian Peter Thiel, he struggles to defend Palantir but express his own privacy concerns: "I didn't sign up for the government to know when I smoke a joint or have an affair," he tells Forbes in an in-depth profile.

His growing wealth has also made it impossible to be anonymous, especially as the company regularly figures in conspiracy theories and has proposed projects that would clearly violate privacy. Even so, he bristles at the suggestion that Palantir has made serious missteps. "We've never had a scandal that was really our fault," he told engineers last month. Of course, if you don't want people to see you as an evil empire, it might help to not name your company after something known primarily as a tool of the dark lord Sauron.