This is an important question. In general, wiki's have
NO security. (That's right!) Because of this, the
possibility exists for accidental or conscious destruction or corruption
of part of all of the wiki.
There are two main ways to devalue a wiki. One is through erasure
and the other is through corruption. Dealing with erasure is not terribly
difficult, because there is a change log (and back versions) of every page
maintained in a location inaccessible to web users. Thus, when page
deletions or major content erasures are detected (which should be fairly
quickly), pages can be restored quite easily to their previous good state.
Explicit and intentional
corruption is more difficult to deal with. The possibility exists that someone
can enter incorrect information onto a page, or edit pages to intentionally
change the information so it is incorrect (for example, people can change
the attributions on a page to make it look like a different person made a
particular comment, or someone can change the content of a paragraph to
alter its meaning in a detrimental way). Pretty much any collaborative system
has this problem. A Wiki is just more wide open to it, since it lacks
any security at all. In practice, wiki corruption is an extremely rare
event, and one that could be dealt with (if needed) with a notification
feature (to a fixed auditor) for new material submission.
In other words, the philosophy of wiki is one of dealing manually with the
rare (exception) case of a saboteur, rather than designing in features
and overhead (both in implementation and in usage) to avoid the damage
caused by a saboteur.