Today I have over a thousand friends on Facebook whom I all know personally. (By the way, Tina, can I add you as a friend there?
It somehow became a list of people I know. EVERYBODY is there. You simply know that if you don't have a persons contact information, you can find him/her on Facebook. I try to distribute my "real" contact information as much as I can, but still often people try to contact me without having my contact information. In that case, Facebook is just unbeatable. (Especially as my personal homepage is for the time being switched off.)
I used to love Facebook's feature to sort the friends list chronologically in terms of when the person was added. So it was not only a list but a chronological list of whom I know. Nowadays that feature does not seem to exist anymore sadly.
In spite of Facebook's huge strengths and opportunities, I do not really "like" it. I would wish that I would be able not to there. Therefore, I don't really "use" it myself actively. I only use it for receiving messages from people who don't want (or cannot) send me an email and for sending messages to people whose email address I don't have. That's it
Why do I not really like it although I consider it obligatory to be there? Well, I guess everybody knows about the objective problems. Subjectively, I consider walls and apps and tabs and photos and whatever else to be pure time-wasters. No interest whatsoever to use those "features" of Facebook. Conclusion: Everybody has to join Facebook because it is truly useful ONLY if everybody can be found there