Earlier quoted context omitted.
> Facebook ... has a pretty substantial moat by way of users 'punishing' each other for leaving What do you mean by this?
I think it's because you might lose contact with people if you don't have a FB profile. If you're not on FB and don't interact with your 'friends' frequently, people kinda forget you exist and stop talking to you, and friendships wither. Even geographically close friendships. Kinda like being ostracised.
I am off FB for more than a year now, and I am just as much in contact with my friends as always.