I can't believe we have to have this discussion all over again

On the one hand, Obama's decision to reinstate some vague notion of the old Glass-Steagall barriers separating commercial banking from investment banking is a disaster that misapprehends the causes of the financial crisis and will lead to higher, not less, systemic risk. On the other hand, while Obama is entirely correct that prop-trading indeed was a cause of the financial crisis, he isn't going nearly far enough and should require banks to spin off their asset management businesses, too.

The truth is somewhere in the middle.

The fine line between commercial banking and the securities business has always been ever-shifting - but the debate was far more sophisticated thirty years ago. None of this is new.