It is only the media itself that is centralized in Nelson's vision. Today it is the giant middle-men that are "centralized" and call themselves "media".
According to Jaron Lanier, Xanadu (Ted Nelson's concept) was all about "two-way" connectivity, not in a trivial sense like client/server websites today but deeply as in a "we're all authors" sense.
> "A core technical difference between a Nelsonian network
> and what we have become familiar with online is that [Nelson's]
> network links were two-way instead of one-way. In a network
> with two-way links, each node knows what other nodes are
> linked to it. ... Two-way linking would preserve context.
> It's a small simple change in how online information should
> be stored that couldn't have vaster implications for
> culture and the economy."
The two-way connectivity was between documents (or actually, pieces of media, regardless of type), not in the "we're all authors" sense (the latter was common back then, and in fact the early web browser was also an editor and server).
The Xanadu idea was that if a link was created from A → B, it would be visible in B as well. They have some cute 3D renderings of XanaduSpace on their website that makes it clearer: http://xanadu.com/XanaduSpace/btf.htm
Lanier further claims this would make Google redundant (since you'd "just see where most of the links led" - it's not clear to me how you'd do that without processing (ie, scraping with a bot) all the documents and their links), and also Facebook because, apparently, what we were missing is a way to see who is linking to our content, so we can "meet people who share out interests" (personally, this is what I see forums or Reddit being used for, whereas Facebook was primarily about people you knew personally).
According to Jaron Lanier, Xanadu (Ted Nelson's concept) was all about "two-way" connectivity, not in a trivial sense like client/server websites today but deeply as in a "we're all authors" sense.
https://en.wikipedia.org/wiki/Ted_Nelson