The foreclosure crisis that erupted four years ago has claimed more than five million American homes—about 10% of all homes with a mortgage. It began in lower-income neighborhoods and has spread to some of the most exclusive addresses in the U.S. The seeds of the crisis were planted a decade ago when banks, discovering the high returns from selling bundles of securitized mortgages, relaxed lending standards and originated millions of adjustable-rate subprime mortgages. Such loans were designed to allow just about anyone to get a home loan. When interest rates on the adjustable-rate mortgages finally climbed, many borrowers began falling behind on their payments, leading to the first wave of delinquencies and defaults.