They are the insurer on up to $45T in credit swaps. As the credit market contracts (it has to, there is no choice) the insurance has to be paid out on one or the other. They are part of the problem, just like the bond insurers were part of the MBS problem. Keeping them around extends the problem. Letting them die risks complete financial implosion. Two bad choices, so we naturally chose the later badness.
Does this mean the US govt has taken that role, are we on the hook for the $45T of credit swaps? Have we taken on that risk?