This is an accumulation of different causes that ended in this crisis, the government can deregulate: then the government bares responsibility of this, but when the banks take too high risks on the backs of all americans who are customers there (a bank has a public responsibility as well as a private one) then they need to be held responsible as well.
It seems that large banks failed in their public responsibilities: are they not accountable for that?
Like if an engineer builds a bridge it has also a public and a private responsibility: if the bad construction of his bridge causes deaths, damages then the engineer bares full private and public responsibility for that.
We don't know specific stories of what the specific banks all did to cause this, their have been major screw-ups from within the banks. It is important that the responsible ones for this don't just run away with it, the press hasn't done its job in giving full coverage of all this & investigation into it.
I'm not sure what high risks you're talking about. The derivatives they are stuck with were rated AAA at the time they bought them, so that can't be what you mean. The high risk (of foreclosure) of some of the mortgages they sold and bought were not really high risk for them since there was a ready market in which to sell them. What is truly stunning is that hardly any of our banks and hardly any of the banks in the rest of the developed world and hardly any of the governments in the developed world seemed to realize that sooner or later the real estate bubble would burst and all these "safe" investments would lose value, although even if they had realized this, I don't think anyone would have guessed AAA rated bonds would lose so much of their value so quickly.
I think it is described in this article:
"By pushing all of this excess credit into the economy, the Fed created a housing and mortgage mania that Wall Street was only too happy to be part of.
Yes, many on the Street abandoned their normal risk standards. But they were goaded by an enormous subsidy for debt. Wall Street did get "drunk" but Washington had set up the open bar."
The Bush Economy - WSJ.com
It is obvious that the government made mistakes, but it is even more obvious that some companies made huge mistakes. Lehman Brothers distracted most of the attention, because of its bankruptcy but many forget the other responsible ones. Why are they not accountable?