Last time people walked away, some are still being chased for the short fall.
Bankruptcy was for 3 years and you were examined in open court.
This time we have the Enterprise act 2002, softer Bankruptcy laws.
If you find your self in a situation where you owe more than the house is worth and repayments on the mortgage, credit cards, loans, HP etc. are making it impossible. You could Bankrupt yourself and walk away from the lot, or after all the unsecured debt has gone you might find you can manage the mortgage again.