So what happened after The Great Unfriending? Facebook became a whole lot more usable as a particular kind of network — the one that lets me see what actual friends and family are doing, including those who are far away… Except for my teenaged daughters, of course, who don’t even use Facebook any more, preferring to spend all their time on Tumblr and Twitter. That’s just one of the things that should worry Mark Zuckerberg, I think.