Hi orda,
I'm not sure the guillotine was ever an American device!
Where the bankers have broken laws, then I would see them face the consequences. I think some of them have. I am not certain they won't face prosecution.
But where they have not broken the law, I wouldn't have them face penalties. It's one key basis of the whole Western system of freedom under the rule of law that you are not liable for acts which were not illegal at the time they occurred, regardless of the consequences.
It may seem a regrettable thing in certain instances. But a law that permits post hoc criminalisation is worse than the problem you have identified.
In this case, the American people voted for a system of government which had few regulations. They (and everyone else) reaped the consequences of that. I guess in your model we should be putting all the Republican voters in jail as well! In my model, it is time for the US voters to wake up and stop making the same bloody mistakes over and over.