Official mirrors

You should have official mirrors with some rules (ex. no ads), and point wikipedia to them, like a wikipedia.google.com, wikipedia.aol.com, wikipedia.archive.org... At long terms this will reduce bandwidth, general service costs.

There's plenty of them. Actually, most pay to mirror out countent on a live basis (this should be that ~400 000 $ income in the financial statements, mainly by Orange, I suppose).