I was just thinking of this the other night...
Perhaps the mining pools aren't everything they are cut out to be...
What is stopping me from:
1) Joining a mining pool.
2) Modifying a miner to only send the "shares" to the mining pool. (And get paid for each share, like everybody else).
3) Send only the "winning" hashes to the Bitcoin network myself. (And get paid for each block that I solve!).
I would therefore be contributing absolutely nothing (except difficulty 1 shares) to the mining pool, only "stealing" from it in a sense.
Slush and/or tycho... can you prove that this practice is impossible?
The block that you are working on from the pool includes the 50BTC payment (for generation) going to the Pool's address, not yours. If you change the address, the hash isn't valid anymore and won't be accepted by the network.