Honestly, if FB was just me and my mom I'd probably get more value out of the site. Smaller radius is better IMO.
Pruning my friends improved my experience, but they grow back over time as people rediscover you or you make new acquaintances. I wonder if you could make a game or website that forced you to prune your facebook friends down, perhaps by looking at your social graph and telling you that you haven't messaged with a person in x years or something, or that you've never even "liked" something they posted. Some heuristics…
https://www.cnet.com/news/delete-10-facebook-friends-get-a-f...