Reading this AP article about a Credit Suisse banker who was arrested in Brazil for helping rich Brazilians escape their own taxes reminded me of a panel discussion I heard last year. The link has audio for all the speakers, and I particularly recommend Raymond Baker's presentation.
Basically there are a hundreds of billions of dollars that are stolen from the developing world every year and invested in the economies of wealthier countries. Legitimate financial systems are used for a lot of these investments, and the total figure is probably several times larger than all foreign aid funds. It's a huge problem, and a commitment to development should include doing something to fix it.
