An obvious example would be WikiWikiWeb. A less obvious choice would be the WorldWideWeb--each site is more or less independent from the rest, but collectively the whole thing functions to represent some metaviewpoint. I suppose that would be the viewpoint of humanity and warez d00dz, but that's life.
Clearly a HyperMedium itself is valuable for organizing information in certain ways. A collaboration, on the other hand, is a little more dicey. Not all information deserves or needs to be held and maintained by more than one person. But much information truly requires a society to give it value. For instance, scientific discourse is built on peer review and academic reference. Indeed, TimBernersLee built the WorldWideWeb specifically to link academic papers together.
In general, we've found as a species that humanity works best in groups. Strength in numbers, and all that. Where one person falters, another will pick up his slack. That is where collaboration is necessary. To ratchet us above our own personal foibles.
However, collaborations aren't perfect. Societies are infamous for providing ten negative forces for every one positive force. Many community models ultimately destabilize, especially when they scale. It would hardly seem different online. Indeed, they may be exacerbated with weakened accountability and large scale.
The MeatballMission is to deal with these problems.
See OtherHypermedia for a collection of such things.
So, communication does not imply collaboration. Collaboration requires working on a task or tasks together. Although any conversation is a collaboration, in some sense -- hell, any relationship whatsoever -- there's an implication of conscious action to create an artifact in collaboration. --EvanProdromou