One of the eye openers for me, as an economics student, was the idea of Pareto improvement: the elegant (if not always realistic) notion of an improvement that leaves at least one person better off, without leaving others worse off. Who'd be against such a deal? The catch is, of course, that Pareto improvements often require some ex-post redistributions.
Here is a very nice Vanity Fair article by Joseph Stiglitz about (in his own words) "an inequality even the wealthy will come to regret":
http://www.vanityfair.com/society/features/2011/05/top-one-percent-201105
Also check out this