> Have they not heard of Betfair, which has been allowing this kind of thing since 2000?

Is Betfair really the same thing? Everything I heard about it while reading about prediction markets made it sound like the Vegas bookies that Cantor is being contrasted against - a limited set of bets run at specific times. Not arbitrary dynamically-generated bets at arbitrary times in the game. To me, that's quite different. Like the difference between a video game which is a shooter on rails, and _Halo_ with decent AI bots fighting you.