Steven Pinker's new book, Enlightenment Now, has a pretty compelling section on wealth/income inequality. The basic position - and I think the data supports this - is that it really doesn't matter what the top 1% are doing so long as the bottom half are seeing improved living conditions.
Furthermore, wealth isn't a static I win/you lose proposition - much of that wealth has been created in recent history. People spend less as a percentage of income on food and housing, have better access to healthcare, and more leisure time than ever before. It's a remarkable story.
Over a billion people have been lifted out of poverty over the last 30 years thanks to globalization. I think that's much more important than how much money Warren Buffett or Bill Gates have.
Income/wealth inequality has been the state of humanity for all of recorded history, and it seems unlikely to go away any time soon - it's trivially easy to show how wealth accumulation occurs using game theory even if trade is relatively fair. The only events that seem to reliably reset the balance are global wars, huge famines, or natural disasters.
I think it's a natural human inclination to fixate on the rich and to demonize them, and perhaps some are deserving of such demonization, but it doesn't seem to be a terribly useful way to think about improving the human condition. It just spurs on class resentment which is, if history is any guide, just about the worst way to go about things possible.