The rel=”nofollow” microformat tag has been lauded as one good way to prevent spam in blog and social media software. Blog commenting systems can easily by taken advantage of, with spammers putting up dozens of links. Same goes with wikis and social news sites. People can simply put in a lot of links, and enjoy the SEO benefits. Therefore, a lot of blog software (like WordPress, etc.) automatically append rel=”nofollow” to every link in the comment threads. Some bloggers actively use rel=nofollow in links in their posts. Even Google advocates the use of nofollow.

The nofollow tag basically tells Google not to spider the site being linked to. The format is simple–just add rel=”nofollow” to any link tag. For instance,

<a href="http://www.googletutor.com">Google Tutor</a>

becomes

<a href="http://www.googletutor.com" rel="nofollow">Google Tutor</a>

Recently, other search engines like Yahoo! and MSN have followed suit in adopting this microformat standard. This way, when your site links to another site that is “nofollow,” the link is not followed by the search engines. There are three effects. First, Google does not consider your link to that site in its computing for pagerank (or other relevant ranking metrics). Second, the search engine bots will not crawl that site for indexing–unless other sites have linked to it with a regular (i.e., not “nofollow”) link. Third, the search engines will not take that link into account when computing for your site’s trust rank (i.e., whether or not your site is a “link farm.” This is much like rel=”aff” for affiliate links).

However, there is discussion in the blogosphere today that the nofollow microformat is not doing its job in preventing spam–particularly blog and comment spam. nonofollow.org has a list of 11 reasons why nofollow is not effective.

1. nofollow does not prevent comment spam
2. nofollow is confusingly named
3. nofollow harms the connections between web sites
4. nofollow is not useful for humans, just for search engines using PageRank or a similar technique
5. nofollow could be used to shut web sites out
6. nofollow discriminates legitimate users as spammers
7. nofollow heists commentators’ earned attention
8. nofollow could be used to further discriminate weblogs
9. nofollow prevents the Web from being a web
10. nofollow eliminates the dissemination of free speech
11. nofollow was developed in privacy with only search engines companies taking part in the discussion

Here’s an explanation on #1, from an extended list of 16.

NoFollow is intended to reduce the incentive for spammers to target blogs. However, for it to be successful, it would have to be implemented in a critical mass of blogs (nearly 100%), which will never be the case. Spammers don’t take any notice of which blogs do and do not implement nofollow, nor which blogs are well moderated and which aren’t, or have any other form of spam protection. Yet the fact is that spammers still target thousands of blogs in the hope that a small percentage will get through. Nofollow is attacking the problem at the wrong level, and never had any chance of being successful.

Another basic reasoning for the case against nofollow is that it makes linkages unbalanced. Take the case of popular or A-list blogs, for instance. They are linked to by thousands of other blogs, and yet they rarely reciprocate–manually or automatically via trackback. Even if their blogs’ trackback mechanisms link back, these are usually nofollow.

Then of course, it’s not the humans who really benefit from nofollow, but only the search engines. And then there is the problem of the search engines not understanding the context behind a link. When you read web content, you don’t really check whether a link is nofollow, right? But then as a human you would understand why that URL is being linked to, based on the context.

Still, there is no consensus as to whether nofollow is really dead. For now, plugin-makers for various blogging softwares have released their own versions of plugins that would suppress the automatic inclusion of rel=”nofollow” in links in blog comments.