A perspective from America:
The mortgage crisis (which many point to as the root of the financial crisis) has led to significant negative equity for many here in America. Many people were sold inappropriate mortgages, and many people over-stretched themselves to buy houses they had no hope of affording long-term.
The government has spent a tremendous amount of time and money convincing banks not to foreclose on people who couldn't pay mortgages due to job loss, debt, etc. (no facility here for paying interest on mortgages for those who need temporary help.)
However, it seems that many decided to exploit that leniency, and chose to stop paying on their mortgages (when they could afford it) because of negative equity - knowing they would probably not be foreclosed upon/evicted.
Many believe that a significant part of the 'recovering' US economy is down to people who have simply walked away from their mortgages, but continue to live in their homes. In the meantime, these consumers suddenly have their monthly mortgage money to spend on clothes, holidays, beauty treatments, restaurants, etc., and so the retail economy has been significantly stimulated making things appear far better for citizens than they really are.
The government is now starting to crack down on that 'loophole' and those people will not be able to buy property again for a very, very long time and will in many instances be chased for the amounts owed (if they could afford to pay and chose not to).
Will be interesting to watch what happens because many thought they were being clever by walking away from their negative equity. It appeared initially they could simply default with no consequences.