Banks who bought CDS protection from AIG could, and did, hedge against failure of AIG by buying CDS protection against AIG default. So where’s the problem?
The problem facing the banks had AIG failed has less to do with their $ exposure to AIG and more with their position exposure to AIG. For example, let’s say I buy $100mm of protection from AIG and then I buy protection on AIG to hedge against the case of AIG’s bankruptcy. Let’s say AIG does in fact go bust. In the ideal scenario the collateral plus the AIG hedges offset exactly my CDS MTM exposure against AIG, then the banks don’t actually lose money. However, the problem is that they are now long risk $100mm of protection (because their $100mm short risk position against AIG is now gone). What happens then is the market realizes that a dozen banks have massive long risk positions in much of the same trades that they will all now try to hedge at the same time. Spreads blow up and the banks lose.
There is much more in this interesting article.