MAX_MONEY is pretty much what it sounds like. This means that the actual maximum supply of SuperCoin is 150 million, not 50 million. Furthermore, the maximum PoW coins is 50 million, rather than the claimed 18.2 million. The 150 million number appears twice in the code, so it can hardly be considered an accident.
That's retarded. How the fuck are you able to run an exchange, if you can't even figure out the basics?
MAX_MONEY doesn't indicate maximum supply, it's a check value for transaction validity.
In the asiacoin hidden premine, I believe these constants were used to trick the blockchain explorer et the wallet code which give the total number of coins.