Occasionally someone will enable a new gadget and make it enabled for everyone with the ability for individual users to opt-out. It would be nice if MediaWiki somehow notified the user (when visiting Special:Preferences or via e-mail or in some other way) that a new gadget had been enabled (without the user's consent) and explain to the user how to disable the gadget, should they wish to.
Even a "New!" tag next to newly enabled gadgets might be sufficient. I'm not sure. The current practice of silently changing other users' user preferences seems fairly unacceptable, though.