G-o-o-d-L-o-r-d no! Not another lame "capitalism is bad" analysis. Sheesh.
Look the biggest question is this: Who are the poor? Who are the rich?
The standard counter-cultural argument is that we have the poorest 20% of the population that needs our help and it is only justice that the richest 20% quit being dicks and cough up their fair share. After all, fair is fair, isn't it? They shouldn't have taken it in the first place.
Several studies have shown that the number of people who fall into the poorest 20% of and richest 20% of the population are not there 10 year later -- only about 10% of the people in either group. The greatest single indicator of wealth? Age, marital/relationship status and education. So if you are an 18 year old male high school drop out you are going to be poor, but this has nothing to do with the fact other than you really don't know enough to make money. People in stable relationships generally are also more stable financially. Older people (think about your grandparents) have good financial resources because they have been accumulating wealth for decades. There is no rocket science here, nor is some imposing economic theory needed to explain it (or more accurately, explain it away).
More to the point -- this means that roughly 4% of the general US population is structurally poor or rich. (Think about that, 4% of the population is driving the entire welfare/tax structure and social programs for the other 96% of us.) The categories of richest/poorest quintile will remain simple because there are numbers involved, but the membership is anything but fixed. Again, a lot of these class analyses were valid in Europe in the latter part of the 19th century when the peasants were moving to the cities, but are championed almost daily in the US press as revelations. If you went to a university in the US, you not probably equipped to discuss economics unless you really are in expert in it. Service courses (Econ 101, e.g.) probably left you dumber than when you started...
The "Tea Party" movement as well as the Occupy X movements are two sides of the same coin. The wealthy = older people who really feel like they have worked their whole lives and are getting the shaft for it. The Occupy folks who are younger but, for the first time in history have been so poorly educated about how the world works and money they really are baffled by any collision with reality. They will not be nearly as successful as their parents because they frankly don't have any idea how. (Ummm that lit crit degree is, indeed worthless and your $50k in loans shouldn't have been given to you. A stint working as a greeter at Walmart is about all you are truly qualified to do).
The graph is not surprising and antagonisms will follow age lines more than race or gender lines.
Oh, there is a very interesting book I want to read (don't have the title in front of me) that argues that wealth is even less stable than in times past, so people stay in that upper 20% a lot less longer than in the past, for various reasons. This has a very alarming consequence if we take good old Marxist class struggle as a model for wealth. (I.e. that there is a static class of "the rich" who are institutionally unassailable, mostly modeled on an enfranchised nobility. The state is therefore the only power capable of taking money from them and as a matter of social justice, must.) Taxing the rich for their money is going to start failing as a long-term strategy since their will actually be too unstable a base to draw from. Think about that before you soak the rich because the really rich aren't are rich as you think and they don't stay that way for more than a couple of years. The tax brackets will have to start falling on mostly older middle class people who will resist. Add into that curbing their Social Security and raising retirement age and you'll get an even bigger brouhaha.