With just a little bit of coordination, everyone can just move one house to the left and leave the banks holding the bag.
Awesome.
...adding, to make it clearer: Someone owns a house with a mortgage they either can't afford or don't want to keep paying (maybe it's about to go up, or maybe they just don't want to keep paying it). They plan to buy the now much cheaper house across the street, and since they have good enough credit someone might be happy to lend them the money. After moving to the reduced rate home across the street, they plan to mail the keys of their old house to the bank.
