A much better use of resources, but you shard the data amongst potentially untrusted hosts (ie, anybody can stand up a lemmy instance and start hosting posts/comments, and then get sick of hosting it and delete their instance and all the uploaded data).

Federation only allows access to the network of servers, it doesn't protect the data at all, which means at any moment an entire community of useful historical information could just be wiped away (especially since there's currently no monetary incentive to continue hosting, its only being done out of desire to be part of the network).

I guess I'd rather see the blockchain (or simpler caching/mirroring) approach, something like the torrent network, so that no single person has access to delete content. We can all choose to not view or not mirror content we don't agree with, but nobody can single-handedly own or modify the data