What is wiki?
In simple terms, it is a webpage that can be edited by anybody. Such webpages always have an [Edit] link that goes to the edit page.
Who needs wiki?
Wiki is a method of information gathering, allowing the voluntary participation of everybody.
What is an example of a wiki page?
The most popular is http://www.wikipedia.com/
What are the drawbacks of wiki?
Well, it's all great that anybody can edit the information on a webpage. It allows for ensured accuracy, since any incorrect information can be corrected by the next guy. But this whole idea depends on the good behavior of the visitors to that webpage. But what happens if somebody decides to descend on the website and maliciously delete posts? Think about that.