From Gregg Easterbrook (scroll down past all the NFL BS)
When you buy a home using a mortgage, you don’t own the home: The lender is the owner until the loan is satisfied. You can’t lose something that does not belong to you! Suppose you buy a $500,000 home, then can’t make the payments and must leave. That would be a huge, awful setback for your family. But you have not “lost” $500,000, as commentary suggests — that $500,000 in value would not have belonged to you until you paid off the loan.
…In most cases, a person who forfeits a recently purchased home will have paid only a tiny fraction of the appraised value of the property, and thus will suffer relatively small out-of-pocket losses.
When you finance 100 percent of your home, so that you have zero equity, there is a sense in which losing your home means losing nothing.
Thanks to Craig Newmark for the pointer.