I am a software engineer. I haven't held too many jobs, and have attended very few interviews. As an interviewee, I always gauged the enthusiasm of the interviewer before 'unleashing my talent'. I have had my share of insipid interviews where the focus was on API specifics instead of ideas and larger pictures. I politely excused myself out of the building mid interview when I realized they needed just a code monkey, albeit with experience. Seizing control would have been a total waste.

I have also conducted my share of interviews. The biggest turn off for me is when candidates try too hard to impress, either by listing out insignificant contributions to FOSS they have made, especially when not asked, or wearing their supposed geekiness on their sleeves. The worst are the self declared nerds and geeks, who speak, look and act in a way that covers all the stereotypes floating on the web. Its worse when, out of turn, they bring up a cool thing they 'hacked'.

Generally, going beyond job interviews, I think the need for being alpha is ridiculously amusing. I am no psychologist, but it smacks of overcompensation and utter lack of self confidence. I avoid such people in life.