Bjorn Lomborg got it into his head that the problem with much global activism is the lack of prioritization. We have finite resources and infinite wants. So it makes sense to address bigger problems first. Would you rather cure AIDS or solve world hunger? Would you rather have clean water or clean politics (reduce corruption)? He got a bunch of scientists and economists together to create a prioritized list called the Copenhagen Consensus. Apparently the best possible thing we can do with international resources is combat AIDS. The site notes:
Combating HIV/AIDS should be at the top of the world’s priority list. That is the recommendation from the Copenhagen Consensus 2004 expert panel of world-leading economists.
About 28 million cases could be prevented by 2010. The cost would be $27 billion, with benefits almost forty times as high.