Wikis are an interesting tool for sharing information with others. The primary difference from a blog is that users don't just comment on the original post, but they can edit it. This has virtue, if your desire is to build a shared deposit of information with a community to verify and correct that information. It's drawback is that it is harder to trace the development of the conversation and compare the views of one person with another. It can be cumbersome to sort through the history for changes and differing points of view.
There is some controversy about the value of wikis, like Wikipedia, as sources for student research. One study in 2005 by Nature magazine claimed that Encyclopedia Britannica's accuracy was better, but not vastly better, than Wikipedia, but that study has been criticized by other researchers. The competing arguments are really philosophical in nature. One side argues that work produced and edited by scholars who are experts in their fields is more accurate. The other side argues that information which is written and edited by a sufficiently large community is self correcting. The first side does not take into account the ways in which a larger community might enrich our knowledge by sharing their differing perspectives. The second side rarely discuss the sources from which the community draws its knowledge in the first place, or how they are to arbitrate a difference of opinion.
The fluid nature of Wikipedia has also been criticized, because it can fall victim to the bias of its authors and political competition, notwithstanding its public policies of neutrality. Wikipedia has actually developed an arbitration process for dealing with serial editing, where people with competing views keep editing an article, one after the other, to reflect their personal views. In the last presidential election, partisans from both parties were found editing the entries about the opposing side's candidate in unflattering, and purportedly untrue, ways. These problems are exacerbated by the fact that not all contributors to sites like Wikipedia cite their sources, as regular encyclopedias do, so it is more difficult to verify the accuracy of the information presented.
One positive result of the dialogue about the nature and value of wikis in general and Wikipedia in particular is that it highlights the subjective side of knowledge in general. While we talk about the "facts" (remember the TV detective who used to say things like, "just the facts, Maam"), we know that facts can be interpreted, organized and presented according to our personal prejudices and ideologies. Most historians, for example, recognize that "objectivity" is beyond our reach, as we interpret the past according to our own culture, ethnicity, gender, religous tradition, etc.
One of the individual Wikis I explored is called MuslimWiki. What interested me most was the fact that it openly admits its partiality. It states that the wiki takes a pro-Islamic view and postings which are anti-Islamic are not allowed. This is a refreshing honesty, since I--with an admittedly cynical air--believe that many wikis are hosted by groups that ensure the information posted does not conflict with their views. When you read blogs and other websites by groups like Evangelical Christians and Atheist groups, you often find comments by the "opposition," sometimes nasty comments. But I explored some wikis on these topics that lacked that element. Makes me wonder . . .