Surely a feature that would be good for external mirrors.
Best would be to secure it and run it as hourly or
half-day cron-job.
Advantages: Mirrors will be kept updated, only the last
version will be delivered for very often edited pages.
Disadvantage: History will be incomplete
Example:
http://tomk32.homelinux.org/mediawiki/index.php?title=Spezial:Export
Note that for now only namespace 0,2,4,6 and 8 will be
exported
the diff