Comment by deeringc

It's possible to build an identity system that can assert certain properties about a person (eg. "older than 16") without revealing any other details about that person. Similarly, it's also possible to build such a system where the identity system can attest these details without knowing which website is being accessed. That way, the social media site (or whatever other "adult" service) can validate the user is old enough, while the identity system doesnt track who is using what.