From James Kwak of Baseline Scenario.

Middle class wages have been declining for ten years and stagnant for thirty years, and if you have a financial system that allows people making $15,000 a year to take out $400,000 mortgages, I don’t think that’s the fault of the guy making $15,000. I think it’s the fault of the financial system.

But, let’s say I’m a guy who makes $15,000 a year. I realize, wow, I can get a $400,000 mortgage and I can live in this house for a few years, and if housing prices go up, I can flip it and I can actually make a couple hundred thousand dollars. And let’s say I’m really clever, and I say, if housing prices go down, I’ll just walk away and I will have gotten to live in a really nice house for three years at no cost to myself. I mean, that’s the worst, most cynical spin you can put on it, right? But this is exactly what people on Wall Street do. The person who is criticizing the janitor for doing this is the same person who thinks that businesses should exploit every legal opportunity to make profits. So even if you attribute the worst possible state of mind to the guy making $15,000, he’s still just doing what any businessman should do under the circumstances. But our national ideology somehow doesn't allow us to think about it in those terms.