In all the uproar about Wikipedia adding "nofollow" to external links I haven't seen it mentioned in the multitude of angry blog posts that it's a MediaWiki software default setting. Most sites running the software haven't bothered to turn it off.
Administrators of wikis that use MediaWiki software versions 1.4.2 (released 2005-04-20) or later have to explicitly set a configuration setting to OPT OUT of using "nofollow" on external links. Most well known wikis I've looked at have NOT done that. Citizendium.org is an honourable exception. Its founder, Larry Sanger, made sure of that personally.
The online manual for MediaWiki has a page, Manual:Combating_spam, which states:
Under the default configuration, MediaWiki adds rel="nofollow" to external links in wiki pages, to indicate that these are user-supplied, might contain spam, and should therefore not be used to influence page ranking algorithms. Popular search engines such as Google honour this attribute.
You can switch off this behaviour on a site-wide basis using the $wgNoFollowLinks configuration variable, e.g.
$wgNoFollowLinks = false;
In response to Wikipedia's announcement that it was adding rel="nofollow" to external links, Andy Beal started a campaign on the Marketing Pilgrim blog to reduce Wikipedia's PageRank to zero. Here's what you need to do:
<a href="http://en.wikipedia.org/" rel="nofollow">Wikipedia</a>
I'm taking Andy Beal's advice one step further. I'll use rel="nofollow" for all sites that generate pages with MediaWiki software, unless — like Citizendium — they've explicitly stated that their policy is to disable "nofollow" on external links. Nearly all wikis require registration before users can edit pages, so — unlike Wikipedia — spam shouldn't be a major problem. I'm not prepared to click the browser's "View > Source" menu item at each wiki that's worth a mention. A site without a publicly stated External Links Policy could disable and re-enable "nofollow" unpredictably, on an administrator's slightest whim. There are better ways to deal with wiki spam. See: Blocking Spam in MediaWiki.
Update: 2007/10/04.
Citizendium got careless. They upgraded to the latest MediaWiki version today, and forgot to disable "nofollow" on external links! It was fixed once they noticed the error.
The WordPress blogging system automatically adds "nofollow" to links in readers' comments, although not in the blog posts. Nevertheless, as most WordPress bloggers are aware, that doesn't seem to deter spammers. It may have seemed like a good idea at first, but the rel="nofollow" game is getting out of hand. Now it's being used/abused all over the place. It's time for the major search engines to admit that the experiment was a failure.
