Wikipedia is the online public domain encyclopedia, which has recently surpassed all commercial Encyclopedia services, like Encyclopedia Brittanica. In an effort to combat spammers who edit encyclopedia entries with external links in order to gain Google´s PageRank favour, has implemented the "nofollow" tag on all external links.

Wikipedia has succumbed to this controversial measure, just like all blog services, the blog search engine technorati, and the social filtering site del.icio.us. The measure was originally proposed by Google to remove the incentive for spammers to add bogus comments to blogs in an effort to increase banklinks to their spam site.

The "nofollow" tag disables the link in question from Google's algorithm, basically announcing to search engines that "this-is-not-a-good-link"; the tag removes any PageRank assignment for that link. Google first proposed the "nofollow" for fighting spam on blog comments and trackbacks. Spammers cannot leach pagerank from high PR blogs with automated comment generators.

The measure is a double edged sword for Google though. Google relies on counting links to a website to judge its importance. If webmasters use "nofollow" links which do not count for pagerank, Google will have no links to count. The concept behind their algorithm looses power.

The "nofollow" tag also goes against the central principle of attribution, which plays a critical role, that of currency, for the creative commons and open source ecology. GIven that wikipedia is lives because of the open data and creative commons ecology, this could affect it critically.

Linking out of wikipedia provides attribution to other sources and providers of information; short changing on attribution could reduce the number of wikipedia content volunteers and inbound linking to it.