I rarely see it talked about just how much ego plays a part in interviewing. In fact, I'd wager it plays one of the biggest parts of the interview process. If you get even one interviewer that is bitter, unhappy, on a power trip, or otherwise a sociopath, you're not getting hired. Many folks hate interviewing candidates; it can put them in a bad mood. They're going to take it out on you because it's safe.
Ego issues sometimes apply to the interviewee as well. I once had to interview someone that clearly thought the interview process was beneath them. This person answered every question as if it was a stupid endeavor and we should just hire them since it was just obvious how great they were.
All jokes aside he was not foaming at the mouth or unpleasant when we first started the meeting, and I'm not the quickest one to pick up on subtle body language cues. So your guess is as good as mine.
