http://www.youwalkaway.com/output24/Int ... lator.html
This is a pretty cool calculator to determine if it makes sense to walk away.
Even though I bought my house in 2006 at the height of the housing market, it would take severe long term deflation for it to make sense for me to sell/walk away from my house. I bought in a really inexpensive neighborhood that is still appreciating, even now.