i just had an epiphany about the function of follow lists as being like a consensus hint for replication pattern of data, combined with relay lists.
if you have a relay that you pay a subscription to be able to write to it, it makes sense that the relay would proactively real-time subscribe to other relays where relevant events may pop up, in the background, if other relays also use this "pull-subscribe" pattern they automatically replicate like a programmable replication algorithm, when the relay has some set of users, their events and relevant events are all received in real time.
each relay then becomes a replica with high availability for its users most requested data, and each overlaps with copies going across the multiple relays that the user has configuration.
each of the lists is different on each relay and the data goes exactly where it's wanted, automatically, all using built in protocol primitives and a simple background service on the relay.
this enables nostr data to be widely distributed and replicated in accordance with the preferences of the users, all automatically and instantly.
it's just about designing the queries and adding the service and relays become a mesh for user data.