Interesting study noted by Ezra Klein. He wonders about correlation and causation, but frankly, if this is true, does it matter? What difference does it make whether assholes become rich people or rich people become assholes? It's an interesting case where the causation doesn't matter, only the correlation.
That being said, it seems a little too convenient to be true. I can definitely see how being an asshole entails feeling like you are more important than other people, and conversely how being placed in a position of privilege makes you think the normal rules of decorum don't apply to you, but these squeaky clean conclusions just don't ever seem to work out in practice.