Funny how when a corporation defaults on its debt and files for bankruptcy so that it can break union contracts and pay workers less, it's seen as a sharp business move, a recognition that their expenditures have come to surpass their income in a structural and unsustainable way. But when an individual decides the same, perhaps after coming to the conclusion that an investment in a home or university education wasn't as lucrative as it seemed it would be at the time, people start thundering about the moral necessity of paying back loans.
We warn the reader in advance that the proof presented here depends on a clever but highly unmotivated trick. -- Howard Anton, "Elementary Linear Algebra"