The numbers are generated completely randomly, and then the SHA256 hash of the game data is generated and displayed to prove that the game board has not been altered during the game. The game cannot predict which square you're about to click, and cannot change it mid-game (or the SHA256 hash would change, indicating fraud). Therefore it can be proven to be simply poor luck if you hit 5 bombs in a row. By using random numbers in this way, eventually someone could double their money 5 times in a row.
Worst argument. Who knows from what you calculate your SHA256....
SHA256 is calculated from game data. If you mean you don't know the secret seed part of game data - well, there are no known collisions in SHA256.
I'm ready to bet 1000
that nobody will post 2 different gamedatas with the same sha256 hash. Let's time limit this bet by 2014.
So, results of each game are provable
. For the fair
part - in theory it is possible for the site to observe playing habits and patterns in visitor's gameplay. Precomputed gamedatas may be used in attempt to exploit this. But that's another question…