While there’s an ever increasing trend by worried webmasters resulting in more and more sites nofollowing all external links, it’s not necessarily necessary, or even beneficial, won't increase your PageRank and probably won’t help your rankings either. So, I’ve now removed the nofollow tags from the external links on my site, including blog comments, as hyperlinks are an integral part of the web. As I have a WordPress blog I used the NoFollow Free WordPress plugin, as it has some handy features and saved me the time I’d otherwise have spent hacking my installation. Of course, I may have to reconsider this policy if inundated with spam, and will be more selective than even about which comments to allow, but rather than be cynical, I thought that I’d give it a go. You can view my SEO blog here.
Oh cool, the only thing you need is a good spam protection service and make sure all your comments are moderated first. Otherwise Dofollow isn't a problem.