Finding the right wiki software

Sometimes people ask me what wiki software to use.  The short answer is "I don't know."  But I can't say that.  So usually, I ask these three questions:

• Are you willing to pay for it?
• Do you want to host it yourself?
• Do you want to hack it?
  

Generally, with that information I can point them at one of the handful of wiki packages I know about. If you're willing to pay, you're usually in a different class than people who want to hack it.  I personally use Kwiki, for example, because I can hack it and because other people hack it, I don't mind hosting it myself, and I'm not willing to pay.    For people who want a professional, hosted tool, I usually recommend SocialText. 

Today, I found a tool that might help me answer that question for people a little more comprehensively.  WikiMatrix lists 21 wiki packages.  Click the radio buttons next to the one's you're interested in and press the button, you'll get a click comparison matrix that compares the tools on dozens of feature points.   No coverage of commercial (or maybe it's hosted?) wiki packages that I can see (JotSpot and SocialText aren't there, for example).  Even so, this is very useful and I'll be pointing people at it.