The housing crash has come to this: With so many Americans owing more than their homes than they're worth - in some cases hundreds of thousands of dollars - more are debating walking away, or halting payments they can afford and waiting for foreclosure.

Statistics don't exist because no one declares their reasons for walking away, but a handful of papers have suggested that there's something to the anecdotal reports about borrowers "strategically" defaulting on their mortgages.

A...