First off, my field is computer science (data mining and machine learning). I have noticed/observed that many individuals who have secured tenured track faculty positions recently had, while in pursuit of their PhD, done at least one internship. Based on this observation I was wondering:
(a) Is it necessary/expected that, to be a top candidate for a tenure track faculty position, one should have at least one internship under their belt?
(b) If not necessary, to what degree does an internship positively impact the chances of getting a tenure track faculty job?
(c) Given the answerer's (your) response to (a) and (b), what is the thought process associated with observing the internship experience on a job candidate's CV (e.g., "This individual worked for company X and therefore, if this person is hired, our department will have better ties to company X.")?
-- As a quick note: I'm talking about an internship at major labs such as Yahoo!, Microsoft Research, etc.