I agree with PAVEBRA.  There is obviously no WMD's but now that we are in Iraq we have a duty and obligation to stabilize the country seeing as how we toppled their government in the first place, not to mention the promises of democracy and peace we have made to the Iraqi people.  But on a more selfish note (America's safety and well being), we need to stabilize the country as a message to every terrorist group threatening America.  We have the power and will to oust you from whatever country you inhabit and restore peace and prosperity to that country once you are eliminated, which could do much to terrorist group's morale.  If we pull out without stabilizing the country it will leave a power vacuum that most likely will be filled by Iran who wants to destroy Israel (our ally), develop nuclear weapons, who is funding terrorist activity in Iraq, and recently has had members of their military captured in Iraq (what are they doing there I wonder...hmmm).  It's no secret that the president of Iran wants the U.S. to leave Iraq so his country can step and "stabilize" it (i.e. setup a puppet government or worse anex it). 

Leaving Iraq while it's a complete mess will only serve to embolden America's enemies.