[danijelb]

Current federation looks like that, a bunch of small independent communities focused on a single topic like tech or photography or whatever, but it doesn't have to be like that. If federation catches on then the most likely the pick will be between 5-10 huge general instances run by corporations.

In such world, Twitter and Facebook could add support for ActivityPub, Google and Microsoft could build their own, different ISPs and media companies could run their instances, and so on. Then the benefit of choice becomes more clear - who do you trust the most to provide you an account. Basically, it would be like the situation with email where most people use a 3-4 biggest services, but the ecosystem is open to new competitors.

The current state of federated social networks is very experimental. If it catches on with big corporations 90% of people will use that, and these small communities can still survive but would be more or less irrelevant.