If every one in the country walked away from a home that was under water, then we would be in an even worse mess than we are now! You agreed to the price of that home when you purchased it. Yes you assumed that you would gain equity over the years. And you still might. Real estate is a long term investment. If you can still make your payments, whether you want to or not, than you should consider staying in the home.
You have a contractual obligation with the bank to pay your mortgage. You were okay with that a few years ago, it shouldn't change now. Trust me when I say I am in your same boat, I bought my house in 2006, along with the rest of my neighbors in a new development. We are all under water, but if we all walked away, then what would happen!?
Try talking to your bank and see if you can get a principle reduction. This might help you feel more at ease. If you are financially qualified to pay your mortgage and do not have a legitimate hardship then they might not be willing to reduce your principle. But you could also ask them about a loan modification to reduce your interest rate, which is likely higher than current market rate.
If you are not in a financial hardship, then you will likely not qualify for a short sale, and walking away should not be even part of the mix unless you have no money and the bank refuses a short sale.
Hang in there and if you need to move prior to your equity rising, talk to your tax accountant about renting the home as an investment property.
We all need to take a little bit of responsibility if we ever want our economy to move forward.