I'm of two minds on this, frankly. Sure, the "we broke it we bought it" logic seems sound, but that only makes sense if our continued presence is actually good for "the Iraqi people." I put that in quotes because despite the platitudes and mixed metaphors rolling off of Tom Friedman's tongue, presumably our continued presence may be good for some Iraqis and less good for others and there is no single metric one can use to determine this.
But, anyway, I tend to suspect our continued presence won't actually be good for "the Iraqi people." Whistle-Ass and the crew don't have a clue. So, I could spend my time doing what the left wing and well-meaning right wing hawks keep telling me to do, and uselessly try to lobby to "make things better," while knowing full well Wolfowitz of Arabia isn't going to do anything that might actually make things better. Or, I can simply say it's time to get the hell out. Note, getting out really implies that the UN would move in and take over one way or another so it isn't about letting chaos take over.
I say we go.
Just one more thought - the other disturbing argument for why we need to stay and prove we can do it right is the old chestnut about our national pride, or our world stature, or our moral integrity, or whatever. Look, we already threw that shit out the window. No need to make it worse.