Wikis - to be or not to be

I feel quite divided on the subject of wikis. It would seem that they are most useful when they are local and controlled, such as a wiki for organising a conference, or a particular program. Another useful application is that of Antioch University, where only  the staff can edit. Otherwise some control must occur. The best known wiki would have to be Wikipedia, and how many people are engaged there in the editing the incoming entries - and still with varying results. One the examples suggested to view, Montana History Wiki, is not open for editing, and why should it. Who is to say the edit will be correct, when it is not known where it comes from. But then why have it as a wiki? The whole wiki looked as if it should have been on their website.
Obviously there are untold thousands out there who love the whole idea of wikis and the community spirit they are to engender - sharing knowledge for the greater good and building groups of like-minded citizens etc etc. I have no doubt that they can and do serve a useful purpose, but perhaps best with limitations of membership and considerable management.