So, contentious title out of the way, I'll explain...
Wikipedia is the best known example of a wiki. This is the frame of reference many use when thinking "what is a wiki". But a wiki is just a word document, online. That's about it. It doesn't have to be anything other than a place people can write things without having to email the document they wrote them in to one another. So in developing an encyclopedia, Wikipedia has inadvertedly created a mass misunderstanding as to the value and potential usage of wikis.
Wikis can be used for absaloutely anything at all which probably currently happens via email like non-standard agendas, standards, reports, current effective practice, policies, reviews, knowledge assets etc etc etc.
Unfortunately, many companies begin their wiki experiments by trying to create the definitive knowledge asset on, say, knowledge management. This is a big ask for people who've never had their own contributions edited by someone they don't know. It turns people off, and prevents them from recognising the potential in wikis. They need to start with a simple and non-threatening activity like a progress report or lessons learned review. Even a shared agenda would help as I said in this post some time ago. Starting small will really help people gain confidence enough to start working on bigger projects like knowledge assets.
Instead of creating company shaped Wikipedia replicas, maybe we should all set our sights a bit lower and take some time to get used to what Forrester and many others consider to be high value tools for business.
And just for the record, I think Wikipedia is the dogs thingamees :-)