@Fa5t3r - I think the problem is that companies are so large and so impersonal a lot of the time. People who are perfectly lovely when you get them on their own are still going to be willing to go along with things that aren't all that ethical, particularly when they only ever see a part of the whole.
There's also that theory that the person most likely to become a CEO is a psychopath, just because of the way they confidently take charge and ruthlessly deal with problems.
When you add up the people who are willing to be ruthless and the people who are willing to look the other way, it becomes something quite scary. And that's why we need business ethics, as clearly stated guidelines, so that we can point to companies that are doing the wrong thing and make them stop.