When you go to "/c/books" on any server, the default should be an agglomeration of all /c/books on all federated servers (notwithstanding the already ongoing defederation wars)

The -USER- then decides if they want to filter by whitelist or blacklist, the user decide what server or community@server goes on the list. Realistically, users will just follow other user's lists, which should be sharable easily. You might even subscribe to someone else's blacklist/whitelist and get updated automatically.

But none of that is possible if the baseline view is not the ability to "see all /c/book on the entire fediverse in its raw unedited form". You can filter out data you can't access.

Whitelists, of course, are poison were just just deem everything to be garbage except "the chosen ones", usually handed down from above by your betters.

A public blacklist model would be much better. You could then build your own blacklist by scanning all user profile for what is on their blacklist and use that as a basis for building your own blacklist, this is mostly how spam filters work. Because in the world of email, if you say "everyone I don't already know is garbage" well, then you might as well just abandon email entirely.