For many people, the mortgages they took out before 2008 are so high that they would be better off walking away from their houses. That is called "jingle mail," returning the keys to the bank and saying, "You can have the house. I can buy the house next door that's just like this for 20% less, so I'm going to save money and switch." That's what someone like Donald Trump or a real estate investor would do. But the banks are trying to convince the mortgage debtors, the homeowners, not to act in their own self-interest.