It's easy to blame the banks but don't forget that the people who were buying this crap were being paid millions of dollars a year for their "expertise." This is not a boiler-room stealing pensions from little old ladies. This happened in the board-room. The buyers were the one's who failed their fiduciary responsibility to their clients (i.e. the little old ladies who rely on their pension).
The reason pension funds, etc... would buy this crap is because they are underfunded and they need to generate impossible returns to meet their future payouts. We shouldn't give them a free pass on underfunding their liabilities and then blindly taking on extreme risk to make up the shortfall.