I take the view that the non recourse nature of the loan is a loan feature just like all the other fine print. Fine print that the bank will not hesitate to take advantage of if it is to their advantage. Handing over the keys and walking is a business decision, not a moral one.
I view staying, forcing foreclosure, and stalling the process while not paying as a clear ethical problem.
I have seen some of loan packages sold to subprime borrowers and find it hard to be too sympathetic to the lenders. 0% down on an adjustable at 7% above the index? How could that ever work out well for the buyer? And how could it ever work out for the holder of 2nd which covered the last 20%.