Quoting Jason Davies, from the post of Wed, 19 Jan:
ok...but think 'talking to paranoid Information Systems people who are obsessed with security'. can I tell them there is no security reason to not use wikis, (responsibly)
you can quote me as a paranoid IT consultant that often shoots himself in the foot arguing with paying clients about security being more important than a feature they want (often losing the argument and some PR points, but not before he lays the ground for "I told you so"s).
Mediawiki is perfectly safe. If you are a careful IT manager with free time you can harden it into a chroot and if you are REALLY paranoid you can disable uploads altogether and link images in some other way from external URLs.