Just before Lehman collapsed, at what we now call the height of the last bubble, Wall Street firms were carrying risky financial derivatives on their books with a value of an astonishing $183 trillion. That was 13 times the size of the U.S. economy. If it sounds insane, it was. Since then we’ve had four years of panic, alleged reform and a return to financial sobriety. So what’s the figure now? Try $248 trillion. No kidding. Ah, good times.