I know about the Rwandan genocide because it was in the newspapers and on the news every day that it went on. I've never once read anything about George Clooney being involved in it afterward (whether he is or not). I associate George Clooney with Darfur, Sudan and even that crisis I can't tell you much about.
I don't know if there is UN corruption, if you are dealing with war torn areas, dictators, tyrants, people with a lot of money and power over people who have nothing or very little, yes corruption is common. I don't think that Angelina Jolie is increasing corruption by drawing attention to problems of the world's worst locations. If the refugees or people in trouble get some of the money donated to them it is still better than if the world doesn't give them anything. There is never going to be any perfect solution. I think Angie tries her best, what more can you ask?