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My opinion - if you're posting on blogs/articles purely for SEO value, you're wasting your time. most comment sections provide only "nofollow" links most good comment sections have so many comments that even if the link is "dofollow" the share of influence passed will be negligible However! If you're posting good, useful comments on blogs that are relevant to your business, you are contributing to the process of making yourself a subject matter expert/influential. Others will see your helpful contribution and perhaps follow you back to your own site/blog. If you're lucky, you may even be able to generate some interaction with the blog owner, resulting in new promotional opportunities (guest posting?) or social media interaction. The one SEO side benefit that you do get from good blog commenting is your backlink profile will be more natural with quality nofollow backlinks to go with all your dofollow links. As we've just seen with the Penguin update, the best backlinks aren't just the ones made to "look" natural, but that actually "are" natural! So - focusing your commenting efforts on a smaller number of relevant blogs and designed to help build your reputation (rather than a huge "spray and pray" approach) will be a better use of your time. Paul

First of all, is it a problem for you?  Have you seen random spammy links to your site and a drop in SERP?   If it isn't, don't sweat it.   It would takea lot of time or money for a competitor to create enough bad links to hurt you.  Unless you're in a Hatfields and McCoys situation with a competitor, I think it's unlikely. If you're really worried about it, do a lot of White Hat link building.  At least then you have something to balance out a competitor's sabotage.