Whether or not they crush home prices may come down to what condition they're in. Economists Karl Case and Patrick Newport discussed this X factor on Bloomberg:

“The question on these aging foreclosures is how many are going to be sold and affect prices and how many will be complete losses. Depending on their condition, they could have a big impact on home prices.” said Karl Case, professor emeritus at Wellesley College in Wellesley, Massachusetts.  

The best measure of the influence foreclosures have on the broader market is the 20-city S&P/Case-Shiller home-price index that tracks deeds, including homes sold directly by banks and deals that don’t use mortgages, said Patrick Newport, an economist at IHS Global Insight in Lexington, Massachusetts.