Now don't get me wrong. I think wikis are an exciting tool to capture tribal knowledge, but the danger lies in people accepting it as gospel truth. It is a human failing that we often accept information as truth if we deem the provider as being trustful. Hence, many of us accept uncritically much of what the New York Times reports, but disregard what appears in the Weekly World News as hogwash. Yet there is no reason to do so.
I guess my point is that the key to a wiki's success is its credibility. This means that, while management must provide oversight it must allow the workers to control the content. Another factor to consider is the expense of maintaining a wiki versus the cost of printing and reprinting official policies and procedures. In the end, the argument over validity of content reminds me of the description of the Hitch Hiker's Guide to the Galaxy:
In many of the more relaxed civilizations on the Outer Eastern Rim of the Galaxy, the Hitch Hiker's Guide has already supplanted the great Encyclopedia Galactica as the standard repository of all knowledge and wisdom, for though it has many omissions and contains much that is apocryphal, or at least wildly inaccurate, it scores over the older, more pedestrian work in two important respects.
First, it is slightly cheaper; and secondly it has the words DON'T PANIC inscribed in large friendly letters on its cover.