Is a "big ego" necessary for a tenure-track faculty position?
I think a "big ego", or at least a healthy dose of self confidence, is necessary for survival as an academic. Our jobs are one of repeated failure. Success rates on grants, publications, experiments, and job applications are often less than 10%. In the face of such frequent failures an abundance of confidence is a require for maintaining ones sanity. Further, many departments verge on dysfunctional and there is generally someone looking to push you down to get ahead (I am not saying everyone is out to get you, but there is generally at least one person in every department looking to get ahead at your expense.) Being confident, outspoken and to an extent self prompting is useful for dealing with these people. The difficult part is not being too self confident and too outspoken and being able to admit when you are wrong.