I'm reading Liars and Outliers, by Bruce Schneier, and this is one of the big points he makes in his discussion of how trust and security balance to allow society to function.
There is a huge difference between personal morality and organizational morality, for instance. Even if every person working for Citigroup had been basically moral (in the sense that they wouldn't have committed fraud alone) this still could have happened, and probably would have.
The argument that gets repeated ad nauseum, that things like this are the fault of "a few bad apples", is just plain false. The bad apples certainly exist (especially given that our society and economy reward anti-social behaviors), but the incentive structure is the real problem. It's systemic, there's no getting around that fact.