I could amend that to take the long form.
Any DM that allows Pun-Pun in their game either lacks common sense, is dangerously passive, lacks a reasonably complete understanding of the mechanics of DnD, or is running a joke campaign and doesn't care.
Basically, what senrath said.
Anyways, this hasn't really been a fruitful discussion. Every one agrees that no player could get away with Pun-Pun at the table. The argument seems to be over whether something can work in theory but not in practice, which seems pretty obvious to me.