Blogs, but perhaps subscribers need to provide their public key so that posts csn be encrypted especially for them.
Woke up with that in my head. not sure how viable it is, but tossing it out there.
Discussion
nostr:nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpqalmm38dqfzwtvc7e8wsca3mge2f3etcnzt0r8mu4f2pjv0tqs7lqdx46cg If every post was encrypted with all the subscriber public keys, you'd have no ability to track which subscribers actually use the service.
Zero-knowledge subscription!
I'd pay for it. Maybe. We don't have zero-knowledge payments yet :(