are written by John Cochrane and Luigi Zingales:
"The big banks know the government will bail them out, and they are already bigger, more global, more integrated and "systemic" than ever. They are making huge trading profits—profits that must someday turn to losses. If brokerage and banking are "systemically important," they cannot be married to proprietary trading. Yet the financial-reform plans do not even talk about breaking up this marriage—they hope simply to regulate the behemoths instead."
The whole article is well worth reading for its take on the "blame it on Lehman" meme.