10. Loopt cofounder/CEO Sam Altman

The word you hear over and over about Sam Altman is "will."

As in, he has it — to succeed, to overcome.

Here's what he told Charlie Rose when Google introduced Loopt-clone Latitude: "You know, I'm happy to say that there was a lot of talk about Latitude is going to kill Loopt, and it hasn't even come close to happening yet. I think we have huge respect for Google, but we can out-innovate anybody in the world, I hope, and we're very focused on this. We're nimble, we're quick, and we'll keep delivering a better product."

Y Combinator's Paul Graham puts Altman on the same list of founder he puts Steve Jobs:
Sam is, along with Steve Jobs, the founder I refer to most when I'm advising startups. On questions of design, I ask "What would Steve do?" but on questions of strategy or ambition I ask "What would Sam do?"

What I learned from meeting Sam is that the doctrine of the elect applies to startups. It applies way less than most people think: startup investing does not consist of trying to pick winners the way you might in a horse race. But there are a few people with such force of will that they're going to get whatever they want.