Cynthia Karena reported on using wikis in biztech section of The Age a couple of weeks back. In preparing her article she interviewed me about wikis, and followed up with some questions via email.
Creative Contingencies uses a wiki to liaise and collaborate with our clients. And we also host wikis for other small to medium businesses. Larger businesses will have a communications structure in place, but a wiki is a cheap and simple way for smaller businesses to start working collaboratively on documentation tasks. We use Mediawiki - primarily because it's the same software used by Wikipedia, and many people are familiar with it. If they learn mediawiki syntax, they can also use that on other wikis.