Wikipedia is another group-participation engine, but focused on group construction of authority and validity. Anyone can modify any article, and all changes are tracked; the rules are few — stay factual and unbiased, cite your sources — and recently some more "authoritative" editors have been given authority to override whining ax grinders. But over all, it is still an astonishing experiment in group participation. Interestingly, in Wikipedia, most users seem to believe that the more edited an entry is (that is, the more touched and changed by many different people), the more authority it has. That kind of democratization of authority is nearly unique to wikis that are group edited, since not observation, but active participation in improvement, is the authority metric.