This article is old. February old. But take it in with recent market developments. First RTFA, then come back.
Okay, so the problems these big banks have been having lately is that credit default swaps are proving the debt insurers can't actually cover the debt. It'd be like if you paid insurance for years on your car, but when it was stolen you found out the insurer didn't have the money to pay you.
House of cards...
Wall Street works through a simple mathematical formula: (How much money I want to make) / (How much money I have right now) = x where x is entirely irrational because you cannot divide by zero.
Yeah, isn't it crazy how man created an economic system designed to be guided by an invisible hand, and then to simply make up a bunch of rules to describe how this economic system is going to behave. Then, as surrounding technology changes we don't question how it'll work with those rules and try to find ways to grow in spite of dangers.