Add these words to your vocabulary

You may need them:

Intentional foreclosure. Jingle Mail. Negative Equity. All terms that could be common in 2008.

The point is, there are going to be lots of houses whose value falls below the amount they are mortgaged for. When that happens, many homeowners may just mail the keys back to the bank. Why continue to pay off a loan when it's worth more than the house you're trying to keep? Just go buy another house.