Having a miserable job and thinking that Facebook is largely a waste of great engineering talent are orthogonal things. I think a lot of good knowledge on the scaling front comes out of it, but I wouldn't say that it's the most efficient societal use of our best engineers by a long shot. I think it's everyone's right to choose how they spend their time, even if it squanders their potential impact, but we generally shouldn't feel proud when we squander it.