the risk to the government from a potential default on GSE [Fannie Mae] debt is effectively zero...the expected cost to the government of providing an explicit government guarantee on $1 trillion in GSE debt is just $2 million.
Joe Stiglitz in the recent Critical Review:
The main cause of the crisis was the behavior of the banks—largely a result of misguided incentives unrestrained by good regulation. Conservative ideology, along with unrealistic economic models of perfect information, perfect competition, and perfect markets, fostered lax regulation, and campaign contributions helped the political process along. The banks misjudged risk, wildly overleveraged, and paid their executives handsomely for being short-sighted; lax regulation let them get away with it—putting at risk the entire economy. The mortgage brokers neglected due diligence, since they would not bear the risk of default once their mortgages had been securitized and sold to others. Others can be blamed: the ratings agencies that judged subprime securities as investment grade; the Fed, which contributed low interest rates; the Bush administration, whose Iraq war and tax cuts for the rich made low interest rates necessary.