Just so ya know... Here's a pretty good article explaining MOSTLY why we are where we are right now... says things in pretty easy to understand terms. breaks it down well without losing the basics. There's obv a little more to it but this seems pretty solid. Good read.
http://scienceblogs.com/goodmath/2008/09/economic_disasters_and_stupid.php and the follow up article with a bit more info.
http://scienceblogs.com/goodmath/2008/09/bad_probability_and_economic_d.php#more