The investment banks didn't have to evaluate all mortgages: they should have been _sampling_ those mortgages and evaluating the firms that supplied them with mo

The investment banks didn't have to evaluate all mortgages: they should have been _sampling_ those mortgages and evaluating the firms that supplied them with mortgages however. The wise firm that did would have anticipated problems well in advance. And it was the IBs' responsibility when they retranched high-risk CMO's into 2nd-tier CMOs and then got those CMOs certified by the bond firms as good as gold. That was criminal, in fact, and charges should be filed against the IBs and the bond rating firms as appropriate.