Simply put, I think the charges against Goldman Sachs are weak. Paulson went short the mortgage market and ACA and IKB went long. Paulson was right and made a fortune. The others were wrong and lost one. That is what happens on Wall Street. ACA and IKB need to put on their Big Boy Pants and move on.
If there was any fraud, it was by ACA and IKB management. They told people they knew what they were doing and that they did due diligence on their investments.