I just read Wikipedia's Wales on education: Openness leads to critical thinking and while I agree that 'collaborative knowledge' encourages critical thinking, I do not believe that Wikipedia is necessarily a good example of that.
Academia has a long tradition of peer review from which the concept of collaborative knowledge surely comes but, with the peer-review model comes accountability. The idea of collaboration in order to collect and develop complete knowledge and ideas is great -- and has long been practiced in the classroom. But, in a classroom setting, as in academia in general, there is a strong sense of ownership and accountability. (And even then, in every collaborative group, there is always some guy who does little or nothing while the rest of the group does all the work!)
In such a setting, students are expected to be able to backup their conclusions by documenting their work -- and the sources of their information. In developing critical thinking, it is important for the student to understand the relative value of one source of information over another. All sources should not be considered equally valid. For instance, the evolutionary biologist's view of the world is dramatically different than that of the theologian. Both have valid perspectives but in completely different contexts.
In recent months, Wikipedia has come under fire for permitting anonymous individuals to edit any entry whatsoever. How does this foster crticial thinking? If one doesn't know the credentials of a source (or perhaps multiple sources), how does one judge if their information is of any value. In the most charitable of circumstances, we can hope that if incorrect information makes it into such an entry, that the intentions of the contributor were not in question -- just the same, the information is wrong! And the Wikipedia reader has no way to judge which information from unnamed contributors have any merit.
So as not to cast my criticism on WikiPedia specifically, this problem is charactertics of the Internet itself. Anonymity is prized as a feature of Free Speech which protects those with unpopular positions from ridicule but in fact anonymity denies the reader the ability to judge if the contributor of the information -- whether on WikiPedia, on some newsgroup, or writing on some blog -- has the credentials to know what they are talking about.
Should information be freely available on the Internet -- just as it is in any public library? Of course! But, just as in the public library, where I can read about the author of a book judge if he/she has the credentials required to speak on a particular subject, I should expect to have access to the same level of information about an author on the Internet. If I don't have that access, how can I lend any credibility at all to the information at hand?
Good intentions aside, WikiPedia does a disservice to its readers by presenting itself as an authoritative source of information if it is unwilling to insist on publishing the name and credentials of its contributors.
In a society which largely gets its NEWS from Late Night monologists, we can ill-afford to have the very people we are trying to educate believing that every source of information is equally reliable.