Read this from the treasury announcement. If this doesn't cause a black swan, I don't know what will. http://www.ustreas.gov/press/releases/hp1129.htm Finally, to further support the availability of mortgage financing for millions of Americans, Treasury is initiating a temporary program to purchase GSE MBS. During this ongoing housing correction, the GSE portfolios have been constrained, both by their own capital situation and by regulatory efforts to address systemic risk. As the GSEs have grappled with their difficulties, we've seen mortgage rate spreads to Treasuries widen, making mortgages less affordable for homebuyers. While the GSEs are expected to moderately increase the size of their portfolios over the next 15 months through prudent mortgage purchases, complementary government efforts can aid mortgage affordability. Treasury will begin this new program later this month, investing in new GSE MBS. Additional purchases will be made as deemed appropriate. Given that Treasury can hold these securities to maturity, the spreads between Treasury issuances and GSE MBS indicate that there is no reason to expect taxpayer losses from this program, and, in fact, it could produce gains. This program will also expire with the Treasury's temporary authorities in December 2009.