What was the point of Glass-Steagall? I've heard justifications about banks underwriting a bond and then having the commercial bank buy it, but these justifications never agree on who is defrauding whom. It is very easy for an investment bank and a commercial bank to make that kind of deal even if they don't share a corporate parent ("Oh, you want in on the next big IPO? Well, let me tell you how to get to the top of the list! I just need one little favor...").
Actually, all of the justifications I've heard seem to imply that Glass-Steagall was necessary to criminalize things like fraud and undisclosed conflicts of interest, which I thought were already illegal.