There is a lot of empirical evidence supporting the fact that the rich "own" government, or, more precisely, that politicians vote in ways that are more correlated with beliefs of high income voters than other voters, and that politicians are responsive to contributions. See, for example, the references herein:

http://econ-www.mit.edu/files/6348

Stiglitz is a serious economist and a Nobel laureate, there is data behind what he says, but bear in mind that he's writing this for Vanity Fair and not the American Economic Review.