IMO, the biggest problem is over-leverage. Dubya allowed Wall Street firms to employ leverage of 40-1, where a paper loss of 2.5% wipes out your equity, even if only temporarily.
What say you about the potential repeal of Glass-Steagall?
My father-in-law was the CEO of a large bank and was the typical old-fashioned, risk averse kind of lender. Replacing that kind of guy with an investment banker and injecting into a commercial bank an aggressive investment banking kind of culture would (and did) lead to trouble.
BTW, I was long gone from the business by the time the Act was repealed, but the banks had been chipping away at it since as far back as I can remember.