Many blog site owners now use “nofollow” links to discourage comment spammers from building backlinks to their own websites. Some in the biz refer to nofollow attributes as a “link condom”. By preventing search engines from following the outbound links, “link juice”is not passed on to the spammers' sites, so it is hoped the spammers will post their garbage comments somewhere else.
What are “dofollow” links?
Most conventional websites with static pages will have “dofollow” links because the opportunity for adding comments does not exist for users. If you can provide an article for the webmaster to publish, the site is relevant to your content, and it's an authority site, these links are pure gold. Links that are fully followed out of the site to yours are often referred to as “link love” or a “loved” link.
Pre-Panda, many WordPress bloggers were installing a Dofollow plugin to encourage legitimate comments from their readers. If you look for them, you'll still find “Dofollow” banners in the sidebars of quite a few blogs. You might want to give the URLs a check, but these sites should still offer a backlink search engines follow when you leave a comment.
Other sites allow commenters to earn “dofollow” status by posting several quality, helpful posts that give value to the reader. The NoFollow Free plugin is a popular WordPress plugin that removes the “nofollow” attribute after the specified number of approved posts have been made.
Should I bother posting on a site with “nofollow” links?
I believe there's a danger in getting too hung up with collecting dofollow links. Google is looking for a diverse and naturally developed link portfolio. If almost all the links in your portfolio are dofollow, that's not natural and your links will be suspect.
Even if you're not gaining link juice value from a backlink, it doesn't mean the link is worthless. For example, being an early commenter on a fresh blog post on a popular site means you're likely to start a thread of comments. Ask a thought-provoking question and the author of the post is very likely to reply. Your comment will be highly visible and you're almost assured of getting quite a few click-throughs to your site from qualified human visitors interested in your niche and, as a result of your valuable comment, what you have to say.
Nofollow or dofollow? There can be considerable link value in both.