Pulling out is, imho, even more ridiculous an idea than going in in the first place.

We went in, toppled a government, killed their army, injured and killed innocents, as well as losing our own casualties. We are not going to chicken out, run tail and hide after doing all that. We'd be dooming the Iraqi people to a government even worse than the last, in addition to the social and economic chaos that would occur when we left.

We made the mess, now we gotta clean it up like big boys.