IMHO it is a term that is indeed superfluous.
Why is there a need to point out the absolute obvious? Are we all blind and / or need it drawn to our attention that a person's skin colour is a particular hue? I fail to see what difference that makes anyway.
Unless we are indeed all blind we can see that they are black and if we have any understanding of history we all know at some point everyone who is black has a heritage from Africa. Why do we need that continually pointed out to us?
Digressing slightly, I haven't read anywhere that say, Jimmy Carter, felt the need to be introduced as the 39th WHITE president of the USA. We could all see he was white so there was no need to point it out. Ergo why must we have it rammed down our throats that Obama wants to be the first AFRICAN AMERICAN president of the USA? Is it not enough just to want to be President?
I have no problem with being proud of your heritage, I am very proud of mine BUT I do not feel the need to constantly refer to myself as an ethnicity and neither IMO should anyone else.