Reviewing the post below I realized that it may sound a bit... racist. I certainly don't mean to single out any racial or ethnic group as specifically prone to being poor or not having the skills to succeed. We should always keep in mind that the majority of American poor are white. I want to be completely clear that insofar as any particular group is doing more poorly than another this is almost always due to historical circumstances. Genetics can play a role - like how the lack of disease resistance in Native American populations lead to the downfall of many civilizations* - but I have seen no evidence that it played a role by modifying cognitive ability or behavior or that it plays any role in explaining modern day inequality. Humans are all pretty much the same and if some of us digest milk easier, or lose our Epicanthic fold as we age, or are more prone to rickets than to skin cancer, well, that's no reason why some of us should be rich and some should be poor.
Liberals tend to view the solving the problem of inequality as a matter of making up for past wrongs. Conservatives tend to reject this and argue that just about every group was oppressed at some point and most of them are now doing just fine. Basically, if the Asians could become successful after all the crap they went through, certainly Blacks can too. And if they haven't that's basically their own fault.
Personally I find neither of these arguments convincing. The "making up for past wrongs" view seems dangerously close to logic "blame the son for the sins of the father". To me, if you're going to make any kind of social justice argument it has to be grounded in current modern-day consequences of past injustice. The problem with conservative view is that though you can, for each poor person, chalk up their circumstances to a lack of "personal responsibility" it makes no sense to do this for a group. Ethnic and racial groups do not make collective moral choices. So even if you want to argue that, say, Sicilians are poor because they lack personal responsibility you still have to explain why they lack it so much more often than other groups. It's either 1) a really incredible coincidence or 2) due to outside forces. But if it is outside forces than you can hardly hold them personally responsible for the consequences.
Well... now I'm rehashing old ground. I just want to make the argument that inequality is real, in many cases it's not solely attributable to a lack of personal responsibility, and it's something that society should fix.
*Obviously war-making Europeans had a hand in it too, but let's not sell the Native Americans short: they probably could have defended themselves just fine is it wasn't for the whole small-pox thing.
Update: For a really interesting take on the sticky poverty problem see Ezra Klein. He references an interesting take on poverty from blogger Tyler Cowen a libertarian.