The housing market prior to 2006 became much like the stock market just prior to 1929.
Many people were buying into it and making a lot of money.
Those holding the stocks or properties, payed, or are paying the price when the bubble burst.
So a property being sold for half of what it was purchased for just means that prices are getting back to something near normal and those that bought into it when prices were skyrocketing are getting screwed.
Very similar to a pyramid scheme.