This one is from American Prospect ("The Argument over Inequality"), and provides an interesting complement to the longer article in the previous post.
History, economics and sociology all rolled into one.
That's why I love studying this stuff.
Fair warning: As with most writing in the popular press, you have to take this as one side of a really complex issue. There are some interesting facts, stats and anecdotes presented by the author, but it would be a stretch to call it an objective empirical analysis.