Suppose you're a gamer - You could configure search results related to gaming to be limited to games you own, games you want, the subset of platforms or genres you care about, games your friends own, and so on. It wouldn't be a priority for most search companies to make something like that, but it would certainly provide some value for certain people. Decentralized configuration would allow for communities with given interests to configure and distribute customizations for that audience, in a way that would appeal to that audience. It's not that farfetched of an idea, very realistic both from a tech and adoption POV.
You.com is starting the building blocks of such a thing, but I don't know how far they're going to push the envelope. https://about.you.com/apps/