There’s been a lot of heat and light generated about this, most missing one thing: there’s no reason why Google needs to pay attention.
Google, or any other search engine, can treat links in the Wikipedia pages any way they like — including ignoring ‘nofollow’, applying extra anti-spam heuristics of their own, or even trusting the links more highly.
‘Nofollow’ has had pretty much no effect on web-spam, and now is generally festooned all over weblog posts across the internet, both spammed and non-spammed posts, at that. It’d be interesting to see if it’s yet flipped to mean a higher correlation with nonspam than spam content…
Update: It appears Wikipedia used ‘nofollow’ before, so this is not exactly new, either.