There is a cryptographic way to prevent this scam.
When you go to potentiallyshadylottery.com they generate a random number between 1-1000 which determines if you win or lose. They md5 this number. Also to prevent rainbowtables they add random garble at the end. Now, you decide if you want to just see the random number, or if you want to play.
If you play, the random number is revealed and you can verify that it wasn't by checking the hash. To verify that the distribution is fair, you "peek" at a lot of random numers and check their hashes. If it checks out, you know the distribution is ok. Since the operator can't know whether youll peek or play, there is no way for him to different play vs peek distributions.