From the Fed:
What is the policy objective of the Federal Reserve's program to purchase direct obligations of the housing-related GSEs?
The goal of these debt purchases, combined with the purchases of mortgage-backed securities (MBS) backed by Fannie Mae, Freddie Mac and Ginnie Mae announced on November 25, 2008, is to reduce the cost and increase the availability of credit for the purchase of houses. Purchases of GSE direct obligations are intended to lower the spreads between rates on GSE direct obligations and U.S. Treasury debt, which have widened recently.
RW: Okay, so how are you going to pay for this?
Will these operations be reserve neutral?
No, these operations will be financed through the creation of additional bank reserves.
RW: Enough said.