Shareholders have very little power over the big banks. The bank managers and traders have perfected demonstrating the principal-agent problem (link below). For example, huge bonuses being paid out even as the banks were being torn apart around them. Managers and traders kept arguing that they need to retain "talent", to the detriment of the supposed owners of the business.

http://en.wikipedia.org/wiki/Principal%E2%80%93agent_problem

More simply:

Taxpayers are suckers

Lenders are suckers

Shareholders are suckers

Managers and traders, not suckers.