Here's another thought relating to this post. Our basic notion of social insurance is that each of us is placed, at birth, in a set of circumstances beyond our control. Before birth, we're not able to write insurance contracts that will compensate us for being born poor, for being born with a serious disease or birth defect, or for other possible bad events. There is then some role for the government in stepping in to provide the insurance that the private market cannot provide, by redistributing income from the rich to the poor, providing health care, or other interventions.
The problem we have to deal with is that, as we teach students in Econ 101, prices help to allocate resources efficiently. To a degree, people are rich by virtue of the fact that society puts a high value on their services, and society puts a high value on their services because these are the services society wants. To provide the services that society wants, people have to be motivated to provide them. Becoming a skilled brain surgeon requires time and effort, and people won't do it if there is no payoff.
Thus, what we have here is a very standard economic problem. We are trading off insurance with incentives. The same problem occurs in employment contracts, and in designing unemployment insurance; it's what canonical principal-agent problems are about.
Now, I don't think this is the way a lot of people, particularly non-economists, think about the problem of income distribution. For them, it seems to be all about theft. On the one hand, some people look at CEOs and bankers, for example, and think that these people are rich because, effectively, they have been stealing from the rest of us. As economists, we know that theft is a serious problem. At best, the time and effort of thieves is a pure social loss. This time and effort simply moves wealth around and the time and effort could be put to productive use. At worst, theft provides a disincentive to the productive people. Why work if others are going to steal your wealth? On the other hand, hard core libertarians, for example, are worried about another kind of theft. For them, the government is simply a mechanism for theft. Whoever runs the government can use its power to steal wealth from the people who have it. From a libertarian's point of view, the government is a parasite, and a good parasite can in fact extract resources from its host without killing it.
What are the lessons here? Theft exists, but we should not be too quick to ascribe bad motives to the rich, or to the government. That said, it is certainly legitimate to ask whether some kinds of financial activities, the creation of complex derivatives for example, are more about obfuscation - theft, effectively - than socially desirable innovation. As well, we have to watch our government carefully. Dictators with armies are well-known for their confiscatory exploits, but democratic governments can go overboard too.