The last crisis is rooted in a deteriorating housing market. If the housing market maintained its strength like China's did, no matter how you structured financial products, Wall Street would not have undergone a catastrophe. As a matter of fact, Wall Street traders bet on the underlying housing market, regardless of the complexity of the products. However, the housing market stopped going up.
Counterparty risk is all about the value of collateralized securities. When the value keeps going down, you need cash to make up the shortfall. Lehman had no cash, the Fed had no precedent to bailout an investment bank, Lehman had to go under. Lehman went under, all its assets on the balance sheet were facing liquidity crisis, which triggered the domino effect. The Fed and Treasury had to put a back stop on AIG.
The bigshots at that time were interviewed by the author of "Too big to fail" a couple of days ago. I sympathized them. As statesmen, they had to do something to stop the domino effect. They couldn't do all the things right but it would have been dead wrong if they did nothing. However, the public will never forgive them.