Bloomberg.com had an important article in June about the Government Sponsored Enterprises in which it is estimated that they may reasonably require taxpayer bailouts of $1 trillion in coming years:
Fannie, based in Washington, and Freddie in McLean, Virginia, own or guarantee 53 percent of the nation’s $10.7 trillion in residential mortgages, according to a June 10 Federal Reserve report. Millions of bad loans issued during the housing bubble remain on their books, and delinquencies continue to rise. How deep in the hole Fannie and Freddie go depends on unemployment, interest rates and other drivers of home prices, according to the companies and economists who study them.
Unlimited bailout authority for these failed government programs was granted in December 2009. That's what prepared the way for the idea behind the rumors now that underwater mortgage balances may be reduced by the Obama administration.
Read all about it, here.