Facebook is making its "Timeline" mandatory for all users very soon (putting some in a comic bind), and now tells you every day if you have been unfriended.
Update: Feb. 2
Google will require new users to enable Google+ and encourages existing users to do so. I probably will soon, but I don't have time to "monitor" so many lists of friends and followers. I find it convenient to let all my tweets appear on Facebook, because I would want "friends" to be aware of them. I don't write highly personal tweets.
I still wonder if employers will start telling some associates how they must manage their own Facebook, Twitter and Google accounts, because there are implications and potential conflicts for some business situations.