That indeed was the purpose of provable fairness, but when a site hides the hashes and shows it only after a player requests/click some buttons, it leaves one wondering what goes on behind the closed doors. For a dice site to be truly fair, it should be able to display the hashes before a games, so that any player can verify with the outcome afterwards that there was no fowl play. This was the ordeal of a player http://themerkle.com/999dice-scam-exposed/ They must have had to improve by now because you can now actually leave their "Fair Bets" button open while you roll to see how the server seed hash changes as you roll.