I quit bookface at the end of last year. I posted a message on my wall, but it seems that bookface has become such an embedded part of life that the most common reaction was that it was a joke. I'm guessing it also didn't get much visibility because I deleted most of my network during the 2016 US presidential campaign to get away from the Trump lovers and Bernie bros; one notable component of bookface's feed algorithm is that it doesn't seem to weight social ties in anyway. Consequently, the more Facebook friends one has, the more interactions posts receive, and the more likely they are to appear in feeds with little scrolling. Conversely, I also noticed that when I substantially cut down my friend list, my feed became dominated by posts from people with lots of friends.
Media coverage of bookface and other social-media giants often focuses on their network effects. We stay registered and active because many of our friends are as well. What's likely far more important for user retention is what we call the power of weak ties. Close friends and family with whom you frequently interact are less likely to keep you on a platform because you'll typically have multiple means of communication; it is those to whom you are less close - the 'weak ties' - who keep you tied to any specific platform. Over the last few years, I removed just about all of the weak ties in my bookface network.
In truth, it was just a matter of time before the negative aspects of the bookface experience outweighed the positives. The pervasive data collection and advertising had been a concern for years, but could be minimized through careful management of interactions with the bookface ecosystem and a handful of general tools (Adblock/uBlock, NoScript, DNSCrypt, etc.). SocialFixer and later FB Purity made the web UI usable, but over the past year or so, page loading had begun to drag on and on. Without these tools, the UI looks like it was designed by a braindead skunk, even after it loads. Over the past year or two, this has only worsened, with the pushing of Messenger for all mobile messaging and the pushing of Stories necessitating multiple clicks just to update your wall.
One thing I noticed in particular about using bookface was that it encourages laziness in maintaining relationships. It's easier to send a vague like/thumbs-up click to someone than actually ask how they are. In my experience, this was especially apparent after going through a couple of difficult years. Probably the most important personal aspect of my motivation to quit bookface is that I want to do a better job of actively keeping in touch with people I care about. While this involves moving forward from an incredibly problematic platform for mass communication, I anticipate the more meaningful relationships will thrive.