Thanks for the zap, my first ever! GrapeRank is a catchy name, this is your own project? Any docs?
Centralisation A is better (depending on who you are of course) because it allows for instant and exact duplication of the all-knowing relay by any outside party and without the need to ask permission. So I could run a duplicate of the atproto master relay without needing to ask Bluesky LLC about it. Of course any copying party would need a lot of infra to run their copy (each copy comes with the full history, lots of storage), but at least the mechanism for them to unilaterally make that copy is there. So it’s actually more like ‘distributed omnipotence’ in the sense of multiple distributed instances of the same central view, with the result of the indexing served up as a commodity, like the big cloud providers all sell VMs and cloud storage as a commodity. (You could even have AWS, Google Cloud and Azure each run a copy of atproto's all-knowing relay and sell access as a commodity managed service.) In this view of things, any developer party can bring any algorithm to the table and no party’s algorithm is going to be more data-hungry than any other party’s. So that incentivises app developers to build things that require a fully-indexed view, they hit the ground running.
Centralisation B is where one outside indexer takes enviable command of an indexing market where there is no other means of indexing besides old-fashioned crawling and sorting everything. There exists no all-knowing relay that developers and users with a need can pull from. This type of centralisation does not allow for unilateral copy-paste in the above way. The data, crawled and cleaned by that leading outside party, is proprietary data. Other parties that want to compete are basically going to have to start from square one, crawl everything, and do so at the same cost (which requires lots of in-house infra to compete, not cloud-leased infra). To make an analogy, instead of simply copying an MP3 of a song they have to set up a recording studio, buy the mics, call up the band, get them in, and record their own version of that same song. All of this is very expensive, and while they’re doing all that stuff the market leader is optimising to the point where it becomes extremely hard to catch up. And so eventually competitors settle into niche roles or give up.
Nostr will never have single all-knowing relays like atproto does, so the centralisation fear is that of Centralisation B. At nostr's current size, however, this isn't much of a fear, as the bar to entry for outside indexers, even considering all the ground work, isn't so high.
My take is that the nostr community should priorities use cases where a global view isn't really all that helpful, just doesn't add much. Town-square microblogging, however, is not one such use case.
