In the US such an entity has a legal obligation to act in the best interests of his clients, and can be held liable for failing to act properly. Bernie Madoff is a prime example.

Regrettably, The Authorities often look the other way. Ken Lewis decided (well, was pushed) to go ahead and buy Merrill Lynch even though he knew he was screwing his Bank Of America shareholders. Still, it was a violation of the law and he should have been prosecuted. So while it's wrong to screw clients for personal benefit, evidently it's not wrong to screw clients for the government's benefit. (I don't know what that's called, but it's not "capitalism".)