That is one SPAM that bloggers get when you have dofollow links. SEO Companies have users commenting with different names and have same IPs, or they have the same guy changing names in the future as they get new projects. Most comments are like “very nice article”, “cool post” and others just to get backlinks. Then you will also get users commenting on your announcement post or contest posts that ended over two years ago saying “I wish I joined” … Simply to get a backlink.

Users blogs are also targetted by more spammers who just want backlinks with those invaluable comments. While it is not fair for those who are actually making legit comments, it is the best way to prevent spam. One can honor their best commentators at the end of the month if they like in the post to give credit. There are alternatives to give thanks to your commentators and not invite SPAM.

I feel if someone can contribution regularly and constructively to a blog post, i’ll say “open the floodgates”.

For e.g., if your blog is worthy of users coming in (and posting constructive comments), then its a compliment that someone is eyeing the link juice here. He/she can be converted into a regular commentor (which is recurring web traffic).

For us, we are there to make constructive comments in web design related blogs and we do not just post a “well done” or “cool article” kind of comment just to have a link back. We highlight a dozen of quality blogs (like yours) and trust me, there isnt a lot out there. So what this means for users like us = become a loyal fan of your blog, follow your updates regularly and make constructive posts.

And there have been a few occasions when we even signed up for membership at some of the blogs we commented at.

my 2 cents.

I’ve had to close comments on a post about the Keywordluv plug-in as it was getting spammed a lot for backlinks.

P.S: Dofollow or not, spammers will spam a blog.