I think the hidden agenda here might be that big corps also test for the candidate's a) motivation and b) obedience. Are you the sort of person who's willing to learn whiteboard programming on your spare time, and then tolerate abuse from the interviewers? The type of unethical business most of the big corps do works best with subservient, diligent code slingers.
Is your experience that interviewers "abuse" candidates? I interview candidates about once a week, and I always try to make them feel at ease and comfortable, no matter if they are doing well or not. I would be curious to learn about other people's experiences.
