Quoth Megan McCardle: "I'm now at a lunch talk by Stephen Carter called "The Tragedy of Just War Theory". The most interesting thing he's pointed out so far is that when Americans say "someone should do something" to stop a conflict somewhere, this is almost tantamount to saying "we should do something", because at a most generous estimate, there are four military forces in the world capable of deploying into a conflict zone and shutting down the war: America, Britain, Australia, and Israel. For diverse reasons, the other three are very unlikely to deploy without our support. We're it."
Never mind the many commenters below that post pointing out that the French intervene all the time in their former African colonies. The truth is, you know the last couple times I've heard people say "someone should do something" a lot? Zimbabwe and Burma. And as I've argued on this page, any "intervention" in either place would have been (and would still be) a disaster, particularly in Burma. So I don't really agree with Carter or McCardle on this one. Mostly when people say "someone should do something" it's because they're frustrated that nothing can be done. The danger is that then someone -- the Bush Administration, perhaps -- can subsequently convince them that something can be done, and that furthermore only we can do it. In this case, there's such a thing as too much "can-do" spirit, like the part where we invaded Iraq and one sixth of its population was either killed, maimed or displaced.
Another failure with this point is the lack of appreciation for regional powers or multilateral organizations to undertake action with US financial or military backing. Think UN or NATO or AU peacekeeping efforts or even Ethiopia's invasion of Somalia. These are not "US" interventions per se. They do require US leadership or military support, but neither would they work nearly as well if the US went in alone or instead. (Matthew Yglesias is right on the money with this one.)
And to people who say that the UN-AU force in Darfur isn't accomplishing jack, my point is, it shouldn't be there. (And for all intents and purposes, it isn't.) Until there's a peace deal or a peace to keep of some kind, nobody should be there who isn't in the mood to unleash hell across the horn of Africa and the Sahel when the Sudan splits into three or four countries and every one of its neighbors descends into ethnonationalistic chaos.
So when I read about Darfur, I do sometimes think "someone should do something." But I do NOT mean us. I mostly mean Khartoum and the rebels, because until they can both come to the bargaining table and be reasonable, there's not much to be done by anybody.