It's understandable to want to make a strategic default on a home that's underwater. Businesses do it all the time without any great penalties, why not the consumer? Unfortunately, unless the individual has a decent income and lives in a non-recourse state,walking away from a home is difficult unless they're prepared to file for bankruptcy.
Loan modifications are the first order of business. If the homeowner's credit is good and the mortgage is current, the chances for a successful modification increase. The banks are problematic with getting modifications done which requires patience on the part of the homeowner. HAMP goes a ways towards easing the problem and may be an option.
The other method is to have a short sale. This is where the house is sold for less than what is owed. Usually the seller will have to bring money to the table in order to make up for the shortfall. A major problem that is inherent in short sales is that banks tend to drag their feet on approving the sale, causing the buyer to go elsewhere. Why wait months for an approval when they can purchase a home elsewhere?
The best way to discover your options is to talk to a real estate lawyer. Many variables come into play when it comes to avoiding foreclosure. Local real estate markets will affect the sale as well as how the local banks are handling their workload. A lawyer will be able to guide you towards making the best possible decision.