3. Mining attack: Place a bet as usual. If you lose, try to put a double spend of your bet transaction in the next block you generate. With a few percent of the network hash power, you could overcome the house edge and make a profit. Any decent sized mining pool could profit from this attack now, regardless of betting limits.
Yup, that make sense. You'ld get away with it just one time though before detection (presuming SatoshiDice is detecting these when they occur.) I doubt a pool would risk the negative goodwill on such a stunt.
I suppose the service could apply a delay before the payout transaction when winning wagers are exceed a certain threshold to prevent this, and then also to limit total payouts per-block to a certain maximum, for instance, to limit the potential loss that could occur.
