I see the credit crunch as one of the birth pang for the information age. Currency and markets have always been about faith and ideas, but in recent times this has really gone to the next level. Different perspectives and ideas are radically altering our ideas of markets and value.
(Incidentally, I'm not a stock broker or a serious investor. Do your own research instead of trusting me.)
The "sub-prime" loan crisis itself wasn't just the result of high-risk lending. It was the result of novel structures. I don't think we would've seen the same kind of bubble and meltdown if banks just offered mortgages to marginal borrowers using the traditional model.
The thing is that the usual mortgage lending business developed into a bond market. So instead of the bank giving you money and you agreeing to repay it over time with interest (and a mortgage insurer being ready to cover the bank's loss if you fail), your bank takes your promised repayment and turns it into more money by selling it like a bond. Selling this bond means they have more money right now to lend out to some other person, too. So not only is the bank hoping you'll repay your loan, but other people are investing in the probability that you will pay back that loan. Regardless of how "risky" each individual mortgage is, just doing this makes everything riskier.
Whatsmore, the firms that are investing in these bonds aren't just investing in straight-up bonds. They're playing fancy new games with derivatives. The various type of derivatives allow you to bet on more than just the value of a company going up over time. You can sign a contract that will benefit you if a stock drops in value, for example; or you can sign a contract that will give you money if the stock changes sharply either up or down but won't pay out if it stays stable; or... all kinds of stuff. The sky's pretty much the limit. And that's the problem. This stuff started out as a way to protect yourself against risk (hence the "hedge" in "hedge fund") but now people are using in very risky ways, too.
Derivatives also allow you to play with other people's money. If we're two huge investment companies, I can sign a contract that lets me borrow some stock you own and do whatever I want with it for a certain period as long as I promise to return it; in other words, I can borrow something from you and gamble with it for a while as long as I promise to give it back -- sounds really risky, doesn't it? You can make it even weirder and more abstract, too.
Well, so far most of the regulation of this stuff has worked like this: "Okay, derivatives are really risky and you can end up owing a lot of money on a deal, so you have to have a lot of money before you can get into this game." Of course, this is kinda like putting a bunch of billionaires together at a no-limit poker table: they're going to play for ridiculously high stakes.
So, what's going on here is that new levels of indirection are making it very hard for regulators and regular investors to keep up, while confusing even the people who invented these weird "investment products" just enough to make it really hard to figure out just how exposed you really are.
Did you know Goldman Sachs actually made money during the credit crash by short-selling? The firm literally bet on the market going to shit and won.
-- Alex