To be honest, I haven't been able to find out exactly how the mechanics of such a multipedia would work in a decentralized environment, because the consensus algorithm poses a weakness in defining multiple versions of the truth. It would probably have to be a centralized service, or a very well-thought out decentralized one, but its game theory has been elusive (to me).
The main difficulties are how to prevent sybil attacks and crowding alternative truths with crap, while also preventing sybils from upvoting the alternative crap that is purposefully planted as disinfo, all the while under a consensus system which is already geared towards a majority view and may be able to flag the minority view (any minority view). A game theory mess :P