Speaking from Germany, Facebook is not important in my circle of accquaintaces. On the other hand, a friend currently working in Denmark tells me that Facebook

Speaking from Germany, Facebook is not important in my circle of accquaintaces. On the other hand, a friend currently working in Denmark tells me that Facebook is the de-facto social operating system over there. So it is not a HN / Valley exclusive thing to be ditching facebook, but there are probably regions/groups where the social cost of leaving is higher than the discussions here suggest.