The reason people use their "African-American" heritage to "get ahead" isn't necessarily a racial issue, although it can boil down to one. It's a socio-economical issue. And because of prejudice and the past, African-Americans are more likely to be in the poverty levels of income rather than middle or upper class. Now I am not saying that all African-Americans are trapped there, because many are moving up, which is a beautiful thing. But it's like affirmative action. Trying to correct the past. Giving underpriveleged people the chance to compete with everyone else. Again it's not necessarily the fact that you're black, it's the fact that you don't have as many opportunities as everyone else.
On one level, you'd think "wow they should do away with this it's basically racism" but if you honestly think that, then you are lucky to have the privelege to not have to have lived through what the hardships are that these people and their parents had to go through solely based on their heritage.
Although in progressive communities like cities, there is more acceptance of minorities, sometimes I do think that it shouldn't necessarily be actions to help certain ethnicities, but instead be programs to help out low-income people in general. Which there are plenty of. I'm probably rambling and repeating myself now, but really if you think that the historic and current lives of most African-Americans are on par with yours and that they don't deserve any aid in being able to have similar opportunities with you, then I don't know, I might have to throw out the word ignorance.
And with Barack Obama, I guess it is going by the old standards of our country. "If you're not all white then you ain't white." Also, physical characteristics have to do with the way others perceive you. His skin colour is enough for most people to warrant him as black.
I think that covers the gist of what the original poster was asking.
And then throughout this thread, I saw that people should not be using the term African-American and just use the term American. I don't know, I think it is all right for somebody to use that as their "proper" label. I have no problem saying I am "Asian-American" even though I typically go by "Asian" even though I live in the United States. Also, I saw someone saying that African-American is stupid because it should be Kenyan-American or Nigerian-American. Yeah, that'd be fine and dandy if these African-Americans could actually trace back their cultures, but they can't because of that whole slavery incident. So African-American works well.
But then again, why do we even place so much emphasis on race? For statistics, the census, and to know the genuine make up of our country? Oh well.