Google, Yahoo, MSN, several major blog software services are supporting the implementation of a nofollow link attribute in an effort to quell comment spam. Of course this relies on the owner of the blog or web site to actually implement the tag properly or at all, in order for it to be effective. As far as blogs go, I would expect the 80/20 rule probably applies in that the smaller percentage of blogs recieve the majority of traffic. Those bloggers are most likely to be very savvy to the comment spam issue because of their visibility and involvment. They’re most likely to start using such a tag. But it will take a long time without mass acceptance which appears to be happening.
For more information on the nofollow link attribute and comment spam, here are links to selected posts:
SearchEngineWatch Blog – Google, Yahoo, MSN Unite On Support For Nofollow Attribute For Links
Lee Odden has been recognized as a top B2B Marketing professional by Forbes, The Economist and the Wall Street Journal. For over 20 years he's worked with his team at TopRank Marketing to help elevate the B2B marketing industry through creative marketing programs that deliver more authentic, experiential and inclusive content for brands like LinkedIn, Dell and Adobe. Lee is the author of Optimize and has published over 1.4 million words on his agency's B2B marketing blog. As a trusted marketing thought leader, he has given nearly 300 presentations in 19 different countries on B2B content, search and influencer marketing. When not marketing, Lee is probably running, cooking or traveling.