Just because he decided not to invest doesn't mean he didn't think AirBnB had the potential to become big. It doesn't mean he didn't think they were going after

Just because he decided not to invest doesn't mean he didn't think AirBnB had the potential to become big. It doesn't mean he didn't think they were going after a big market. He might have just thought the team wasn't very good, or the product wasn't quite right, or any of the other reasons investors pass on companies. The potential was there, but it just wasn't very likely given the details of the company. I think what Thiel is getting at with his rule is to not bother with companies that don't have the potential to ever get huge, given their product and market. That rules out a huge number of businesses, so following it prevents you from wasting a lot of time.