I've just received a friend request from someone who I don't know but I've had one question/reply interaction with. In looking at his and his wife's profile I see they are into and organising spiritual healing and retreats and absorbing the cosmic power of pyramids. I've refused it for the two reasons of I don't know him and I don't hold with his interests.
I use it mostly for informational purposes similar to you, Mark. I’m on a couple of Italian citizenship and language groups, etc, plus I follow the local news and the local parks. My children rarely use FB anymore, which was my reason for joining in the first place.
I have turned Facebook into a bit of personal fantasy. Since my real name does not appear, it doesn't bother me to accept new "friends" whenever I receive a request since I don't care what they say or post. It must be admitted that the vast majority of my Facebook friends are members of the cinema and theatrical community of Argentina. Usually, when I receive a friend request from Argentina, I am informed that we already share 8 or 10 other friends. This pleases me because it validates the fact that you can have a totally different life from your real life.
I do the opposite. Everyone of my friend on FB is a real person (meaning i met in flesh) or could be from anyport. I blick all others. Each time i join a group i am appalled at the rudeness or stupidity of comments. So i snipe and leave or get expelled... Lately on a group on history, there was a discussion about a woman who was in the Titanic, boarded a canot and then went back to the ship when told her dog was not allowed. So many people said it was such a gesture of love and would do the same. I said i'd be happy if my wife chose to drown because of a stupid dog instead of surviving and rejoin family. I got a lot of flak. I consider i am right... got told i knew nothing about life, love etc. One day maybe, one day i will be abke to shut up. But it ain't funny to shut up !!!