This is troubling. I'm not much of a gambler, and haven't ever played SatoshiDice, but someone bringing a casino to the Bitcoin community is really not doing their homework to not understand how SatoshiDice's hashing works and why knowing the secret list ahead of time isn't a problem if it's being hashed with the transaction ID.
It is possible for them to rob their investors by sending selective transactions to themselves since they know the secret list ahead of time.
This part is actually true. It is possible for SatoshiDice to deliberately make bets against themselves that they know in advance will win. This will reduce their profits, and result in lower payouts to their investors.
It's not possible for SatoshiDice to cheat against their players though (except by using the wrong day's secret, or just not paying out at all).