When large companies take on risk, then they impose risks on the rest of the system. And these are systemic risks and these systemic risks we never used to think were really that important, but as soon as we recognize how the financial sector - the risks the financial sector takes on can impact the entire global economy, we realize that those risks needed to be controlled for the social good.

The collateralized debt obligation, the CDO, is a structure which allows you to more or less continuously choose how much risk you want to take in a whole batch of securities. And the reason why they got us into so much trouble is that it's hard to figure out how much risk you really are taking.

Risk managers and investment bankers and actually, all kinds of investors took on more risk than they expected. So there was a failure of risk management. There was a failure to recognize how much risk there was in some of these securities that people bought.

You know, some of the portfolios we might consider buying are portfolios which would do especially well if we have an economy-wide, or I mean, a global climate change that impacts us very negatively there are some companies that will do well, and so it might make sense to hold some of those in your portfolio.

If you have information that a company is not as good as its stock market valuation, you don't have a way to sell that stock unless you already own it. And so that information doesn't get incorporated in the company's stock price as fast if you don't allow short selling.

Credit default swap gives you something to do. You can buy some credit default swaps from them to protect yourself against the bankruptcy of people who owe you money.

That is, many times we're not risking our own money, we're risking somebody else's money, or maybe that someone is going to back stop or downside, but we still get the upside.