"They call it 'jingle mail' or something like that. You walk out and post the keys back (hence the jingle)."
Mortgages in the US are different. In the US the mortgage is held against the house, when the borrower defaults, the lender can only go after the house, not the borrower.
That's why they just can walk out and send in the keys by mail, if you did that here in Australia the bank could still come after you to reclaim the debt.
