January 22, 2007
People have been using Wikipedia as a way to get high-pagerank pages linking to their sites. They used all sorts of techniques to spam the online user-created-and-maintained encyclopedia.
So now it has gotten to the point where all Wikipedia links are being marked as “nofollow.”
The nofollow tag was agreed upon by the major search engines to combat comment spam in blogs about two years ago.
The mailing list message about why its being done seems to imply it may be a temporary move…take a look at the email subject:
Nofollow back on URL links on en.wikipedia.org articles for now
Emphasis is mine.
What may not be taken into consideration is that the actual code and database is available for download and used by many sites. Those links have already (and will continue to be) propogated until those other sites change/update their code and/or database.