It struck me this is an entirely arbitrary level of knowledge and people have, culturally, learned quite a lot about online computing in the past few decades. Y

It struck me this is an entirely arbitrary level of knowledge and people have, culturally, learned quite a lot about online computing in the past few decades. You can easily imagine seeing this posted 20 years ago: "Right now I can sign up at AOL.com and get to email everyone else who has signed up - where do I sign up for social networking and do I get to interact with everyone else who has done the same?" There's no reason to think people can't come to grips with a federated model just because they're used to a centralized one.