A little bit of everything you mentioned I think.
Sientific studies seems to show that a human being is not programed to have to much "friends" at once. So when a community grows to much you tend to be exposed to more "strangers"
That's why the "federation system" might be a solution to choose the social environment you are in and feel a better connection to those around you.
Even if you risk to create a bubble of people you agree with.
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