Hello. I know none of the current softwares support this (and that's good), but what stops a person (aside from integrity and will to see pool mining work) from checking each hash they submit to see if it is the solution to the actual block, and if it is holding it for themselves, solving the block, then continue submitting shares that aren't the solution, effectively giving them all their hashing power at a pool, and then also giving them all the rewards they would receive from solo-mining. This would seem especially deadly to PPS pools...
It's very possible, but there is no reward to the person that is doing it. They can't claim the block as their own, so they would only do it if they intended to be malicious to the pool.
