See this Educause article about wikis; hat tip to Many2Many for the link.

Indeed, an instructor could structure and regulate interaction to such an extent that the wiki is effectively transformed into a stripped-down course management system. But doing so risks diluting the special qualities that make wikis worth using in the first place, with the result being, in the words of Heather James, "pumped-up PowerPoint." James has described the experience of using wikis in her teaching as her "brilliant failure." She regrets that she "changed the tool, but did not change the practice," and failed to account for the "great potential in this tool to be completely disruptive (in a good way) to the classroom setting." With the benefit of hindsight, she concludes that for wikis to fulfill their promise, "the participants need to be in control of the content"”you have to give it over fully."26 This process involves not just adjusting the technical configuration and delivery; it involves challenging the social norms and practices of the course as well.