What proof of humanity is sufficient? Today it is a phone call, or a verification sent to a real address (limit one registration per household), or a video call. How will we verify humanity in 20 years when audio and video emulation is foolproof?
We'll have to have in-person attestation or make all services paid, perhaps.
I would wager all services will be linked to a verified credit or debit (non-temporary) card. Most of them are now...
How are you going to connect the physical person with an identity with in-person attestation? Many (several of which major English-speaking) countries don't have mandatory government IDs...
A commenter below suggests that government eIDs could be used. I bet this will be harder to implement and will have much worse conversion rates than (the already terrible) mandatory credit/debit cards... Not to mention the hell that we as non-US citizens will have to endure if anyone tries to impose any form of mandatory ID there... One can only take so much complaining about government overreach about something that is basic necessity here in the EU...
Realistically it will be a government or private service that everyone will have to have to verify that it is a real person. Or at least tied to a real person so that banning will be more sticky.
We'll have to have in-person attestation or make all services paid, perhaps.