I have no idea what drives Twitter following. Absolutely none. I curate my tweetstream quite actively and quickly unfollow people who annoy me, which is nearly everyone. I suspect the world divides into people who haven't used their Twitter account for years and those who use client apps to manage their tweets in a much more sophisticated way than I do. So on reflection I'm not liking my hypothesis that he used to have more. I suspect he's never had that many.