I had a look, it's quite a nice scheme -- but how do you handle one of the secret providers not revealing the hash? e.g. the site is down, they lose the seed etc.

Imagine this,  BitSaloon secretly buys 50% of your tickets, then they have a 50% chance of winning. If they don't win, instead of revealing the seed that would prove so, they lose it (or suspend the site). As I understand it, you'll be forced to do a redraw, which would effectively give them a 75% of winning with 50% of the tickets