http://www.ico.gov.uk/~/media/documents/library/Privacy_and_electronic/Pract...
New rules: only cookies that are "strictly necessary" may be set without permission. All others require explicit permission from the user.
These will be quite a lot of work (to say the least) for commercial sites with ads to comply with.
But UK-based MediaWiki sites should be OK, shouldn't they? Does MediaWiki use cookies for anything other than login functionality? Not sure if the "You must have cookies enabled to log in to SITENAME" bit will need rewording for tediously strict compliance.
- d.