Probably worth clarifying: I don't think Thiel is arguing for monopolies. Instead he's arguing for lack of competition via differentiation (i.e. if you're the only one doing something, you're going to have a much easier time of it).

Also worth noting is that this idea isn't Thiel's, but is one that Michael Porter has been putting forward for years now. Of course, Porter is read by MBA students and Thiel is read by people who want to do a startup, so that may explain why this idea seems so new to people.

P.S. if you're interested in reading more about Porter's ideas I can recommend two books. The first is Understanding Michael Porter, which gives a good summary of the main ideas of his works. The second is Different: Escaping the Competitive Herd, which doesn't address Porter specifically, but covers similar ground.