SatoshiDice does not follow the rules:
The blockchain is a system for transferring value, of which the final total is specified in advance. Those are the terms of the social contract every Bitcoin holder has adopted understanding. Those are the terms every node has agreed to voluntarily participate in the network.
Nodes and miners have not unanimously agreed to have their resources/time spent inefficently processing informational messages like "you lose", "you win", or even "I bet on game with much". This was never part of the agreement.
Nor is the system supposed to hold up to flooding. If you go back to even the original paper by Satoshi, miners are expected to filter out flooding attacks like this. The proposed transaction fee solution works in most cases, but not SatoshiDice because they have social-engineered gamblers into covering the fees for them, and to make it worse the gamblers are willing to pay a higher fee than real users. If Bitcoin had achieved critical mass already, we might have been able to just say "too bad, deal with higher fees", but at this pre-adoption stage the response to that would almost certainly be "screw you, I'll stick with VISA".