The more I think about this, the less I'm convinced it would be a disaster. Bush and co claim it will become a terrorist haven, but no one in Iraq will want Al Qaeda setting up shop after all the cold blooded murder they've been doing to all sides there. An Iranian puppet is the second worst case scenario touted by the Bushies, but would that be worse than when Saddam ruled as America's hated enemy?

So we pull out 95% of our troops. Most likely Iraq would split into 3 sections. Shiite, Sunni and Kurd. (This has in fact already happened with local ethnic cleansing over the last two years.) America should set up a big base with the remaining 5% of our troops in the future independent Kurdistan, put peacekeepers along the Kurd-Turkish border, and make sure the Kurds get the oil territories in Kirkuk. Continue to maintain good ties with the sunnis by making sure they get the oil fields around Mosul, and let the shiite factions fight it out for control of their section.

So realistic worse case we have a Sadr controlled pro Iran Southern Iraq. So be it. Everyone wins and the US is still in the region on a far smaller troop scale and essentially out of the kill zone.