Wikis are sites where stakeholders collaboratively discuss, share, and maintain content.
Because company wikis are often the repository of commercially-sensitive material, we’ve used our own as an example. All wikis need frequent, ongoing participation to be useful.
A wiki needs to be about something. And it needs to have a core of 12 - 15 participants to stay dynamic, though a smaller group of highly-dedicated people can suffice.
Wikis can be plain and utilitarian or graphically-rich. However, ease-of-use is always a critical component.