By the massively higher amount of spam and scams on Facebook, compared to IRL.
I don't step outside on any random day and get immediately blasted in the face by dozens of One Weird Tricks and AI-generated images of Jesus crossed with shrimp.
There’s probably over a million literally deranged people on Facebook.
Even if you only come across a tiny fraction of them, that’s still way more then you could possibly ever encounter in real life, in one physical community, due to simple probability and population density…
And building a thing where you massively increase their reach is a decision, yes.
As an example, it could be Nextdoor-y[1], bound to physical location rather than global. And that's not a stretch either: it's what Facebook was in the early days. They decided to change it, to become what it is now.
[1]: I do not in any way mean to imply Nextdoor is doing things right, just showing that "social network structure" is a decision, not some kind of inevitability.
