Blog commenting used
to be a way that a lot of people used to get "free" links to their website. Nowadays, though, it's probably not such a good idea.
In the wake of the recent Panda and Penguin updates from Google, links from blog comments on low-quality or spam blogs are not going to count in your favor. Blog comment links may also be a problem if they have your keyword in the anchor text (as in, you used your keyword in place of your name when you submitted the comment). Too high a proportion of exact-match keyword anchor text links looks artificial.
In fact, if those are the primary links you have pointing to your site, they will likely actually count against
you. People who have link profiles that look like that have increasingly been finding their sites have dropped off the map, and they're getting "unnatural link" warnings in Google Webmaster Tools.
If you're going to comment on blogs to try to get links, use your real name (or at least your company or brand name) when you submit the comment. Make sure the blog is a legitimate originally-written blog, not just a collection of "spun" articles "borrowed" from elsewhere. And don't rely just on blog comment links for your inbound linking profile. That's a recipe for disaster in today's search world.