The securitization of mortgages is an especially bad idea and responsible for much of the crisis because banks could absolve themselves from one of their prime economic functions, assessing creditworthyness ob borrowers. If the mortgages can move off the balance sheet and their risk hidden in complex composed securities (“Abacus”) rubber stamped by regulators, banks stop caring about credit risk and give just about everybody a mortgage (which is exactly what happened), as they turn themselves into a volume business with no skin in the game (which is exactly what happened)… But apparently we’ve all forgotten these simple lessons.