Warning: this blog post has an extremely high link density.  When I wrote this, there was no article on “Link density” on Wikipedia yet. Feel free to create that article yourself. As of version 2.0 of the Web, everyone is allowed and entitled to do just that. In 1995 (long before the term Web 2.0 was coined), Ward Cunningham made this possible with his simplest online database that could possibly work. He was recently interviewed on the FLOSS Weekly Podcast and his original WikiWikiWeb is still online.
Probably because of its inherent simplicity, the wiki has become immensely popular. To give you an idea of this popularity, here are some crude statistics:

MediaWiki Download Stats
Now you might think: “So, wikis are hot. Thanks for the stats, but what’s in a wiki for me?” A wiki has proven to be a simple and effective tool for building a database of collective knowledge of a group of people. Fruits of a wiki range from solutions to problems to ideas for new products. The added value of a wiki lies in the possibilities that it creates for harvesting collective intelligence (crowd wisdom) and for collaborative innovation. Tim Hyer excellently explains this. I have much trust in the wiki model too. Some time ago, I even played with the idea of applying that model to a country’s civil code. Thinking of adopting a wiki yourself, but not entirely convinced yet? Then watch this 21 episode movie series about wiki adoption (Blip TV).
The wiki certainly seems the easiest way to add collaboration functionality to your website. All you need to do is choose a wiki engine, style it to your company’s style guide and your done, right?. Well…not exactly. You will first need to choose a wiki engine. There are quite a lot of wiki engines that we can choose from, but fortunately, there is the Wiki Engines wiki that provides us with a nice top 10 of wiki engines. You could start by picking a wiki that you can deploy in your back office. There are, of course, more selection criteria. Selecting a wiki engine is just like selecting any other software package. The Wiki Choice tree might ease the selection process.
Once you have launched your wiki, how do you make it work? We all expect to see a flourishing community, but how are you going to convince people that they should submit their knowledge and ideas? In order to grow a wiki needs fertilization (generating interest) and cultivation (monitoring and moderation), so point out a Champion. A wiki, like any other social site, requires substantial investment before you can reap its fruits. Will there be any return on your investment? What does a wiki cost? Maybe you will find answers to these questions at the International Symposium on Wikis (WikiSym) (the WikiSym website is, of course, a wiki).
Finally, here’s a list of 12 wiki’s that actually work. How is your wiki doing? Are you reaping fruits or are you still investing?