Why is Africa so poor?
Because the white man exploited it so much?
Because those Africans can't stop being so barbaric towards each other?
Why??
This is a great and quite lengthy article about the factors of Africa's poverty.
http://globalpolitician.com/articledes.asp?ID=966&cid=8&sid=59
I recently came across it after seeing it linked on a forum.
The site is full of good articles dealing with politics, news and world events so it's worth taking a long look at.

The writer of that article makes a great point, that Africa's poverty cannot be to any one specific reason but to a combination of factors involving both the Europeans and Africans. These factors include the horrendousness of colonialism, the kleptocratic and tyrannic native regimes and leaders, and neo-colonialism.