VK - I think you are correct, a walk away is a walk away. Clap the hands and you are free of the debt. It will follow you on your credit report but what is to stop someone from just walking away and renting for a number of years. With the glut of housing no landlord is going to refuse cash in hand on a month to month lease regardless of someone's credit background.

I think the question is more moral than financial. If you are indeed upside down or even break even then it makes financial sense to walk away. I'm sure that you could even buy a depressed piece of property afterward despite the walk away mark on your credit.