I recently read a chapter from the book "Humble Pi - When Math Goes Wrong in the Real World" that made a convincing case for why CEO pay went up so much and stayed there.
Part of a typical CEOs compensation is in stock options. Prior to 2006, the valuation of stock options was often misunderstood by company boards, and during a period of economic expansion, they began compensating CEOs in what amounted to a lot more money than they realized. Then, a formula was released that allowed options to be valued effectively (the guy who came up with it apparently won the Nobel Prize in Economics). But by then, CEO pay had effectively tripled due to what amounted to years of over-payment in the form of stock options. Thus, it led to a new, unintended high valuation for CEOs, and a "new normal" for their compensation package.
[tl;dr]: Companies now pay their CEOs proportionally three times more than they used to due to a misunderstanding of how to value a particular type of security. I'm sure there are other factors at work, but it was nice to read something other than the "Greedy CEOs are hogging all the cash!" media narrative.