I woke up this morning with what I think is a good idea… I'll write something that analyzes the follower lists and recent DMs on my Nostream relay to determine who people on my relay interact with the most who don't already have write access to the relay. Then I'll white list the top X people on that list.

Which raises a question - when User A responds to User B (publicly or via DM) will User A's client ever try to write to a relay it knows User B uses but which is not on User A's relay list? For example if User B's NIP-05 says their on Relay C, but User A retrieved the message from User B via Relay D, will User A's client ever try to write to both C and D even though C isn't on A's relay list?

Clearly my plan will work if the unpaid user reads from my relay. But it won't be particularly effective unless clients try to respond to all the known relays for the other user.