In a message dated 3/30/2011 9:23:57 AM Pacific Daylight Time,
Shades of past conversations. Being "Does mirroring *an* article, or even
a hundred make your site a *mirror*" ?
Personally I say no. Mirrors are copies, everything is shown.
Copying a few articles doesn't make you a "mirror".
But at any rate, http://meta.wikimedia.org/wiki/Live_mirrors
Seems to show over 150 live mirrors.
I expect the major effort is focused on those consuming the most resources.
That's what would make sense to me from an admin point of view.