On his last day in Italy, the President told African diplomats the legacy of colonialism is no excuse for their lack of prosperous democracies. Then he headed for sub-Saharan Africa, where he'll bypass the undeveloped, politically unstable countries of Nigeria and Kenya -- birthplace of his father -- in favor of Ghana, with its growing economy and recent history of peaceful transitions of power. Why is he going? How is he likely to be received? What's the best way for the developed world to help a troubled continent?