Attention, everyone who thinks the United Nations can be a force for peace, at least as it's presently constituted: your heroes are running away after a few bomb attacks.
I do not bring this up to taunt anyone. (Well, at least that's not the primary reason.) How can an organization that pretends to be the ultimate arbiter of international law, and which has higher pretensions to be a world government and police force, possibly be taken seriously if they're such cowards in the face of relatively minor resistance?
The French, their sidekicks the Germans, and the rest of the hollow men in the Western world generally agree that the U.N. is the proper instrument for rebuilding and governing Iraq. They say they are altruistic, but really it's a cynical ploy because they know a U.N.-administered Iraq will be much more pliant than a U.S.-sponsored rebuilding effort. It would help their case greatly if the U.N. would show some backbone in standing up to thugs and terrorists.
I do think a reconstituted U.N. could be a force for good in the world, but they need to begin by kicking out the rogue countries like Cuba, North Korea, and Zimbabwe. Full membership ought to be reserved for countries which meet minimal standards of human rights and non-aggression towards its neighbors. You say that Cuba won't get kicked out, because it enjoys the support of so many left-leaning governments around the world? You are right, and that is the problem.
Number of people willing to die for their country or religion: millions.
Number of people willing to die for the U.N.: several hundred, but few of them work for the actual organization.
Cost of one U.N. retreat: 2-3 car bombs, sporadic gunfire, scary politico-religious talk.
Cost of one U.S. retreat, as long as G.W. Bush is presiding: not determined.