There were two reasons for killing him: 1. Vengeance. 2. Osama's popularity ratings. But can't you see that this will now result in massive recruiting into linked terrorist groups worldwide? Also the creation of yet another martyr for the religious fanatics will spur them on to more and more atrocities. Surely the best thing was to have left him isolated and powerless inside his dusty compound? How many more 100's or 1000's will now die as a result of this?