> 1. Family joining Facebook. It used to be a funny place I could goof around with my friends, posting whatever I wanted. Now I have to filter everything I say because my grandparents can see it.

Google+ nailed this perfectly. You could place connections into Circles, and a post could be shared to specific circle(s). It let teenagers be teenagers, allowed professionals to separate their personal life and maintain a professional appearance, and so on.

In reality we do maintain separate personas for different groups of people we know, and it's ridiculous that no social network reflects this. The closest anyone else has come to this is Reddit where you can use multiple pseudonyms, so someone recognizing your posts/comments on one account does not get access to all of your posts/comments.