I haven't looked at the Extreme Programmer's Wiki, but I have a little bit of experience with the Mailman (list manager) Design Notes Wiki:
http://www.zope.org/Members/bwarsaw/MailmanDesignNotes/FrontPage.
I think this is a wonderful example of what a wiki can do for a collaborative community. If you login to the Mailman Design Note wiki, you will find that you can edit and lay waste to any page, OR you can just add a comment. Plus, and this to me is THE critical difference between a WIKI and our beloved bboard, and it's a difference that in the right community really powers WIKIs and has them really crushing our bboards, with a WIKI, casual users can do more than just edit/waste a page, they can create entire new sections of the website, or reorganize older sections.
For example, bboard threads are wonderful, but our search engine a bit restrictive. With a WIKI, a user of OpenACS might contribute by regularly spidering the site and creating a permutated index of the OpenACS site, and using the WIKI to host that permutated index as a WIKI page/application at the OpenACS itself. That contribution wouldn't require Don or Ben or Roberto to start or maintain, it would be self generated and it would be invaluable towards finding answers to OpenACS issues. (As an example of a permutated index, take a look at http://www.ilcso.uiuc.edu/Web/Documentation.html#A)
Ben, I believe the value of a wiki is that in fact you do not spend core resources building the wiki content, but you do enable the community to use community resources to create/edit/maintain content for you.
And I am pretty sure with the zope wiki the wiki engine maintains a history of each page, so if a kiddie comes in and wastes it, it can be reconstructed. Pages have owners that can delegate what others can or cannot do to a page. I think there is a diff facilility. And if there's not, well that's something to add to the ACS WIKI.
I have heard requests here and at the opennsd site that folks would like a sourceforge like projects page. A place to announce, discuss, and manage various openacs or opennsd modules. With a wiki in place, the community could create their own spaces as needed, without requiring the writing of an OpenACS sourceforge module. If you believe in ad-hoc self generated structure, the value of rapid prototyping and turn around from requirements to software and back, then I think a wiki would be a wonderful addition to the OpenACS and the OpenACS website.
Well, got to run and take care of the kids.
