The social tagging site del.icio.us has implemented the “nofollow” tag on its home page. Following the example of blog search engine technorati, del.icio.us implements the anti-spam measure proposed by Google.
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.