On: Jimmy Wales gives up administrative privileges after community backlash

That actually sounds like it would be fairly easy to add to the wiki software, and practical as well. You could even just add a cookie to remember people's preferences about adult images, the way Google Image Search remembers your "SafeSearch" preferences for a while even if you're not logged in.

This isn't easy to add actually. The mediawiki software, last I checked, doesn't have this capability and adding it would be a royal pita.