If you want to understand a bit more about what is happening in the markets, I highly recommend the IMF working paper "Money for Nothing and Checks for Free". If you are pressed for time, take a look at the graphic summaries throughout the paper.
Two things strike me in all of this:
1) The leveraged positions on some of these investments (in particular in hedge funds) on securities is almost an inversion of the historical norm of banks with required asset reserves for loans. The fact that these securities were not only over-valued but in some cases are unable to be valued is alarming
2) The subprime loan segment just blossomed a few years back as the economy was coming out of a recession via a major injection of money for the central bank (of course depressing interest rates); after today's rate cut, it's unclear that what Fed policy is going to look like. Could this mean things are really that bad? Obviously the equity markets didn't think so.
PS: Mauro Guillen of the Wharton School pointed me to this paper.