For a while, having a wiki was what all the cool kids were doing. It was the ultimate in collaboration, allowing anybody who cared to edit any page they wanted to to read anything they wanted. Certain high profile successes (Wikipedia for instance) only served to make the idea even more cool. For a time, wikis sprang up everywhere, even for sites where a traditional content management system made as much or more sense.
What people failed to realize at the time was that the very feature of wikis that makes them so useful for collaboration – their wide open editing policies – also makes them wide open for abuse by the less scrupulous types out there. It should not have come as any surprise that open wikis suddenly became the hottest venue for spammers and other nefarious types to peddle their wares. After all, it happened on UseNET, email, forums, and every other open forum.
These days, running an open wiki requires intense oversight from the administrator. Once the spammers find an open wiki, they will hammer away at it until the end of time, adding ever more garbage to the content. Even simply reverting the spam edits does not remove the contents from the wiki which, after all, stores previous revisions which are still accessible. No, running an open wiki requires being able to permanently remove the garbage and that must be done continually.
Of course, most wikis are really targeted at a fairly small community so restricting edits to authorized users is a reasonable solution. But that also requires some oversight from the administrators. If one simply allows anyone who wishes to create an account and start editing immediately, the abuse noted above will sill occur. After all, spammers can register accounts as easily as anyone else. That means there must be a manual vetting stage for new accounts and that requires administrator intervention. And even once an account is approved, the activity must still be monitored and abusive accounts stopped in their tracks.
In the light of all that, is a wiki a good idea? In the general case, no, it is not. Not even a moderated one. Before putting up a wiki, you should consider carefully whether you really need the functionality. Is there a real benefit to it? Are you really just creating a site where people can discuss things? If so, maybe a forum is better. Are you just trying to get your information out and only a handful of people in your organization will be editing content? If so, a standard content mangaement system is probably all you need.
The fact that wikis are fairly rare compared to the number of sites out there should tell you something. And among the wikis that do exist, almost all require some form of authorization before edit access is allowed. That should also tell you something.
In short, wikis (as originally imagined) are stupid. They simply ignore the nature of the population in general.