I watched the movie Margin Call tonight. It is a fictional account of what went on at Lehman Brothers when it collapsed.
A respected financial company is downsizing and one of the victims is the risk management division head, who was working on a major analysis just when he was let go. His protégé completes the study late into the night and then frantically calls his colleagues in about the company's financial disaster he has discovered. What follows is a long night of panicked double checking and double dealing as the senior management prepare to do whatever it takes to mitigate the debacle to come even as the handful of conscientious comrades find themselves dragged along into the unethical abyss.
The problem of course was the mortgage backed securities that tranched good loans with really bad ones. It took time to put these together so the company became very over leveraged. The old risk management models no longer worked as the risk management head and his protégé discovered. The CEO described these "assets" as bags of odorous excrement. Lehman went down but the government could not let anyone else go down so we got TARP. Of course the problem is that the banks are still sitting on billions of dollars of bags of odorous excrement and at some point they will hit the proverbial fan.
Wall Street was attracting people from many disciplines at this time. The protégé that discovered this problem had a PhD in rocket propulsion - he really was a rocket scientist. When asked how he found his way to Wall Street he answered it payed a lot better and it's all about numbers and numbers are numbers.