A lot of people have questioned why we intervene in Libya and not in places like the Congo, where civil war has resulted in the deaths of millions of people. The answer is that the nature of the threat to civilians in general is completely different. A useful analogy: if you have a gun, you can use it to protect your child from a wolf, but not from disease-carrying mosquitoes.
What is happening in the Congo and in many other failed states is a tragedy, but its very difficult for outsiders to stop the sort of low-tech civil war that goes on in places like that. The only real way to do it is to send massive numbers of US ground troops to impose order, and even then its very difficult and politically risky. There are situations in which it should be done anyway (Rwanda) but its easy to see that building up the political momentum for that kind of a mission might take longer than the conflict lasts.
By contrast, it is very easy for the US to stop civilian deaths if we can focus our efforts on a few targets, IE high-tech military forces like tanks and airplanes. Our military is built to deal with such threats. We can get there really quickly, because we have carriers all over the world. It is also far easier to secure political backing for such sorts of missions, since the risks are far lower.
Anyway, I do think that this effort has a reasonable shot at working. If you break the back of Qaddafi's military forces, and get a stalemate, then its just a war of attrition. If we are serious about getting him out, at that point we just impose an embargo on his oil exports and starve him out. Once his cronies realize the money well has dried up they will turn on him.
It is nice to dream of a world where our interventions are purely based on the gravity of the situation in the affected nation, but the reality is we have to pick our battles. We simply don't have the ground forces or the money to occupy every troubled spot in the world. But we do have an military that is really, really good at blowing up enemy tanks and airplanes. So if those are the weapons that a dictator chooses to use to kill his civilians, why not neutralize them?