There are two general uses for Wikis.
1. Collaboration - pbwiki 2.0 layout packs quite a bit of utility in the screen Real Estate and you can turn off the right pane to view more page content on one screenful.
2. One or two editors quickly putting FAQs, instructions and notices on the internet or intranet.
For use 2) the admin ought to be able to switch off everything but basic page content and selectively turn on search, sidebar and change notification.
Perhaps there should be a permission level lower than reader that defaults to change notifications off (or whatever the admin set its to) and allows more config of the screen content.
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