I've a lot of sympathy for people who were given stupid money by banks and I've zero sympathy for banks in such scenarios - especially after what we witnessed during the Celtic Tiger. At the same time I don't agree with people doing stupid borrowing and I agree that people should pay back their debts. (this is a general comment and it's not about the OP)"Handing back the keys" doesn't make any outstanding debts disappear. If/when the lender moves to collect this they're not really "pouncing" in my opinion. The borrower will be well aware and informed that they still have an outstanding debt by the time that this happens.
In relation to this issue, there are going to be a lot of problem cases now as people who came to 'arrangements' after the bust and their 'deals' come to an end (warehousing, interest only etc) then we're also going to be seeing the fallout of 'deals' that have mortgage payments ending when people are 70 etc.