What's the point

At first I couldn't really see the point of wikis. If you want to add some information to the internet about a particular subject, then create your own web page (easier said than done I'm sure). But then I saw the other wikis (I always thought it was just wikipedia) and now I kind of like the idea that other people can add their ideas and thoughts. I looked at the book lovers wiki and thought it great that people can write their own book review (but how can we tell if it's been changed). Then I had a quick browse through the Library Services wiki and liked the ideas that it gives people a forum to express their thoughts, ideas and experiences.