Way of life?
PmWiki main characteristic is modularity. The initial archive provide a very functional but minimal wiki and each PmWiki administrator can configure a whole bunch of things from basic security to very complex included scripts. So what are the guidelines of online PmWiki.org?
From an user point of view, PmWiki.org is incredibly free. Not only the product itself is GPL (probably the most free licence), but the writing on the online wiki is nearly completely free.
Anybody can not only read but write, without any login nor password. even in documentation pages archived for file distribution.
Groups can be created (it's probably not a good idea to do so without real need).
Elegance/Ease of use
pmwiki has all the elegance and simplicity of good open source software. It could not be easier to install on a server, and yet it allows a user quickly to create beautiful web pages. If only all the web were so simple!
So it's up to the users to clear room when needed. If you encounter a clearly out of subject page (advertisement), clear the page, add "delete" as only text and the page will be deleted.