In 2000-2002 I was a member of LunarStorm, a (now defunct) Swedish community where at one time 90 percent of Sweden's high school students were members. What I liked about it was that it gave you much more opportunities to interact with - and get to know - new people; Facebook mostly keeps the interaction to people you know, and you can't really start talking to anyone who seems interesting, or reading what they write and commenting on it without officially becoming "friends" first. But following the writing of interesting people and commenting on it was how I made friends on LunarStorm, many of which I still know ten years later. I miss that. And I don't think you can easily recreate it in the panopticon that is Facebook; having every conversation broadcast to everyone you know doesn't make for a relaxing atmosphere.

(I haven't tried Google+, so I don't know how it works in that respect.)