Pursuit of an Edge, in Steroids or Stocks By ROBERT H. FRANK ASSET bubbles like the one that caused the current economic crisis have long plagued financial markets. But like hurricanes in the Gulf of Mexico, these disasters have been occurring with increasing frequency. If we want to prevent them, we must first understand their cause. It isn’t simply “Wall Street greed,” which Senator John McCain has blamed for the crisis. Coming from Mr. McCain, a longtime champion of financial industry deregulation, it was a puzzling attribution, squarely at odds with the cherished belief of free-market enthusiasts everywhere that unbridled...