I came off it maybe 6/7 years ago after being on it for a couple of years. At first it was good to see how a lot of folk I hadn’t seen for well over 20 years were getting on - where they were living, working, kids or not, married or not, etc. It was nice to know how things had turned out for people. We exchanged a few massages, said “see you around” and that was it really. But it was really good to see what had become of them. I also think that, in those times, there wasn’t so much of the “look how great my life is” type of posts.
However, I finally came off it because I didn’t really like how it took all my lives (work, personal, social, family, etc) and sort of melded them into one. I think we all compartmentalise different bits of our lives - I’m a different person at work compared to how I am with friends........ I still have the same beliefs and principles, but I act professionally, am serious and don’t tend to over-share at work, whereas I like to let my hair down and be much more open with friends. My family see me as a reliable, solid and sensible person 
who just seems to get on with things.
One day I had a conversation with an aunt I was visiting. She’d friended me a while before, although I don’t really think we ever spoke on Facebook. She was asking me questions about photos I’d been tagged in during my uni days in the 80s....... basically photos where I’d been shitfaced at parties and behaving in a way that I wouldn’t have done with family......... I’d laughed at the photos when I saw them as they reminded me of some really good times I’d had, but I didn’t think they were for my family to see. This conversation left me feeling a little bit uncomfortable and that was when I realised that a drawback of Facebook (for me) was that it didn’t let me have my different lives. So not long after that I completely closed my account.
Last year, however, I set up a new account. DH and I bought a house in a village in Spain and we plan to move there when we retire in a few years’ time. We visit as often as we can (not at the moment, unfortunately) and are trying as best we can to integrate and become part of the small community. The villagers have been hugely welcoming and do things like go in and check on the house when we’re not there and leave milk, juice, water, bread when they know we’re arriving.
There are a couple of village Facebook groups, so we joined in order to try to get to know people in the village and also keep up with local stuff (eg announcements from the town hall and the annual programme of events). It has been an amazing tool for us and, especially at the moment, it’s allowing us to keep in touch with our future neighbours.
However, I’ve made a subtle change to my name and put myself down as living there (rather than in the UK). I also used my Spanish email address and Spanish phone number so I wouldn’t come up as a suggested friend to folk I know here in the UK. Apart from two people, all my friends are from the village in Spain as I don’t want to go back to the old Facebook where everything was as one. Maybe that seems odd, but it’s just how I feel.
So I guess I have mixed views, but I certainly think it’s been a great help for Spain.