@jennythelib - You make a nice point that this is only a problem if you must move. But if you do, it can be a *big* problem!
Many lenders are willing to work out "short sales." Honestly, I think it helps if you have missed a few payments. Make sure, if you must do a short sale (in which the bank agrees to accept less than the balance on the mortgage), that your agreement with the bank specifies that you will not be paying back the difference.
Another issue to be aware of is the tax implications of whatever route you choose. Forgiven debt is actually considered taxable income! So in theory, if you owe $250,000 on your house and the bank lets you sell it for $200,000, you will owe taxes on that $50,000. Ouch!
In some years, the government has provided tax relief for first mortgages on your primary residence, but I wouldn't count on that continuing. Talk to an accountant - getting out of the hole with your bank could put you in a hole with the IRS!