Totally agree with your point about zuckerberg. Zuckerburg evolved over time, but the culture did not, to my knowledge, radically diverge from zuckerberg. Facebook as a whole made that same cultural journey to maturity, which I think only reenforces the point.

Re: "founders can change" - I don't think it's the role of the staff to wait around while a guy spends years in management learning not to be a dick. If they put up with it, and it happens, fine that's great, but it doesn't impact the linkage between CEO and culture.