I'm being recruited by a big tech co probably on the basis of my GitHub account which doesn't state my age. Also assume they haven't looked at my Wikipedia page. Should I respond? At what point should I disclose my age?

Update: Raines Cohen, in the Facebook thread, came closest to my own take on this: "If they are not hiring you based on your experience, connections and reputation, you will be totally wasted there so it won't last, you wouldn't put up with being a mindless corporate drone. If they are, that's where it gets interesting."