IED sounds like a good analogy to me. Semper Fidelis
BTW, his staying there is not going to make the foreclosure process last any longer. It would probably even save the bank money because it will keep it off the vacant building list.
Tough situation. If he is going to walk away, at least let him know that he can still live there for a year without making payments. Maybe that will help him bounce back a little. Depending on the lender, he may even get a check for moving out when the REO agent takes it over and offers cash for keys. I've seen cash for keys checks over $2,500.