rel="nofollow" attribute on HTML anchors was supposed to help prevent comment spam. Unfortunately, as Michael Hampton explains at length, NoFollow hasn’t worked – at least not based on the volume of comment spam that Akismet has removed since I moved to WordPress (519868 spam comments detected as you read this post).
Randa Clay has created an alternative – the I Follow Movement – sites that acknowledge the contribution that commenting makes to the blogoshere (avoiding the need to specifically add links to a blogroll in order to spread some link love). I figure that if NoFollow is not preventing comment spam, the least I can do is let the information people leave here in comments work for them in the search engines (at the risk that a few spam comments will still make it through).
Following Owen’s example, I’ve implemented the DoFollow WordPress plug-in on this site so URLs in comments will now (hopefully) be picked up by the Googlebot, Slurp, MSNbot, Teoma and others. Incidentally, if I specifically add
rel="nofollow" to a link, it still works – so it’s still possible to block links that you really don’t want the bots to follow (robots.txt directives are unaffected too).
So, please, comment away – and consider doing the same on your site.