Cristian Mezei’s SEO Blog reports an interesting observation:
http://www.seopedia.org/seo-news/google/wikipedia-banned-me-nofollow-this-at-all/

When testing this search really returns the following typical page:

"Sorry, no information is available for the URL en.wikipedia.org"

However, when using 'site:' parameter you'll get some results, entry reports:
http://www.google.com/search?hl=en&lr=&safe=off&q=site%3Aen.wikipedia.org&btnG=Search

Maybe because there is a 301 redirection on "en.wikipedia.org" ... ?

Yeah, that page redirects to en.wikipedia.org/wiki/Main_Page which is listed in Google. And as Google's site operator lists everything "below" that domain it finds stuff.

>> Maybe because there is a 301 redirection on "en.wikipedia.org" ... ?

Hi Tom...

Maybe this will help (it's my response to Bill and it's in the comments, so maybe you missed it) :

>> Yeah, I know Bill. But think about it.. The 301’s landing page should’ve been shown when I search en.wikipedia.org right ?
>> Well it’s NOT. MSN and Yahoo see this issue correctly right ? Why is Google so fucked up ?
>> Is 301 safe anymore ? Or even SEF ? (in Google).