In the May 18-24 Economist's special report on Capitalism theirs a piece called Unexploded bombs, subtitle, Beware of Fannie and Freddie. It says:
Fannie and Freddie " have become arguably the two most worrying concentrations of risk in the global financial system. This is because of their portfolio of morgages and securitisations, their use of derivatives and the habit of many other borrowers, including hedge funds, of using their debt as collateral.. (wow, only one mistake and I didn't even look at the keys. Look ma, I'm TYPING!)