In Analogy to the WikiPedia what about an AnnoPedia? (AnnotationPedia)
WikiPedia=community built global knowledge nodes AnnoPedia=community built global annotation nodes
Contrasting knowledge -> annotations are (hopefully friendly constructive conversations i.e.) exchange of opinions, critiques, suggestions, motivations, ..
Even on the WikiPedia and some other wikis there are special "discussion pages". In my opinion such pages are the ideal candidates to be annotations, organized by a WikiAnnotationMediator.