To add context, the reason I say this here is to provide a gateway to the first implementation of the relay.tools API. Friend lists are important and the question you pose is "where and how should they be stored?"

To me it makes sense to offer NIP-05 verification and NIP-51 friend lists at the domain level. Consider this a domain's "operational relay." From there, users have a realm to explore local relays while maintaining a universal aggregation of users and content.

Some people may want to host different configurations of operational relays depending on their goals. I don't expect Amethyst or relay.tools to decide what every configuration should look like. But, I imagine some users are content in taking a Damus-style approach, while others might prefer to segregate their data across multiple relays to ensure they can cater to every use-case and community goal they have in mind.

nostr:nprofile1qqs8eseg5zxak2hal8umuaa7laxgxjyll9uhyxp86c522shn9gj8crspz9mhxue69uhkummnw3ezuamfdejj7qgjwaehxw309ahx7um5wgerztnrdakj7qgawaehxw309a5x7arjd9nksarwdamjumn0wd68yvfwvdhk6tct9vymn I hope this makes sense lol