What caused the financial crisis?

If you ask people where [financial] risk will flow, there are two camps. One says risk will flow to the smartest person, the person who best understands it; and the other [camp] says risk will flow to the dumbest person, the person who least understands it. And at least based on my experience and my understanding of what has been happening in the derivatives market, it’s the latter. 
—Frank Partnoy. “Money, Power & Wall Street. Frontline. PBS.