I'm imagining the #fediverse being used as a sort of search engine, with a human-sorted index. Like a distributed #DMoz. For example, say users who recommend a novel in a post include the hashtag #goodnovel, and other hashtags for, maybe, author, genre etc. Then another user can search for novels to read across their social network, maybe with the ability to specify degrees of separation.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko