Hi Mona Lisa
Tisza Major's answer was pretty much spot on. When you signed your closing documents, you made a committment to pay back the loan in full and the banks intend to make you satisfy your end of the agreement at the cost of thoroughly wrecking your credit with the club that they wield around known as foreclosure. There are other situations that would possibly qualify as a hardship, such as having to relocate for a job, medical issues, etc..
Also, as Tisza mentioned, the best advice is to consult an expert in your market place that deals with your current climate. Obviously, from an objective point of view, it may well be worth it for you to cut your own losses and get out from the property yourself and make up the difference, as opposed to holding it, or renting it even. Thats just a numbers game however and one you should again, sit down and go over with someone who works in the business daily and can help guide you through it.
One last thing to consider that I don't think Tisza mentioned, is that even if the bank will look at the possibility of a short sale, if you have other assets available to you, the banks are more than able to ask that you participate in sharing in the loss and liquifying some of those assets that are not "necessity." ie, a second home, cash or stock reserves, etc. In my experience, they haven't gone after retirement or things of that nature, but just be aware, that in a short sale, they may well ask and have every right. You obviously do not have to participate, but they most likely, in turn won't help facilitate your short sale.
Hope that helps.