The refinance boom is over and the real estate bubble has popped. More than 30 million Americans' are upside down in their homes with negative equity.

Formerly hot markets in New York City, Arizona, Washington, D.C., California and Florida are now suffering without buyers or even prospects. Many previously booming markets are seeing double-digit declines in sales. In Florida the drop in home prices is staggering, and this has become ground zero for the real estate bust.

When prices fall, and they certainly have, that's a problem. Nationwide . More »