In time we'll see that our biggest problem is mediated communication. Facebook is not a common carrier. They curate, and as they swallow up larger areas of communication they have the ability to impact world opinion and events.
Even if they don't use that power, it is a power that should be checked because it can be abused without our knowledge.
Facebook may curate, but also everyone on Facebook is a curator. They post or like what they approve of. So Facebook is a giant curation engine, but everyone gets to be a curator. That's... rather democratic.
It breaks down when everyone only listens to those who agree with them, of course...
The degree to which your likes and dislikes influence what you are fed is hidden in Facebook's proprietary codebase.
For the most part, feed algorithms are tailored to show you whatever will keep your eyeballs on the screen. The idea that your conscious desires prevail in the realm of allocating your attention has been pretty well debunked by psychology and cognitive science.
Disclaimer: I don't actually use Facebook. Like, at all. I don't even have an account.
But if I understand correctly, I see what my friends post (and repost). And I also see what Facebook sends me that isn't from my friends, based on my likes and dislikes. But talking specifically about what my friends do that I see, each one of them becomes a curator - at least to me. And I become a curator to my friends.
Even if they don't use that power, it is a power that should be checked because it can be abused without our knowledge.
Google and Twitter are in similar positions.