Blog commenting helps to increase the page rank of a site. By commenting on blogs our site may be linked with so many other sites. So i think it is an important method in search engine optimization.

Blog commenting helps bring traffic to your site. As much as possible the comment should be relevant to the post.

I think something is being missed about "blog commenting". The usual rubbish about "blog comment useful way for backlink and traffic" is crap!

I started blogging a couple of years ago and as part of my research on "blogging" I began reading numerous blogs about blogging, SEO, writing, and construction (I was and still am a contractor). Through commenting on several of these blogs (adding my opinion, asking questions, and replying to other comments) I also was able to build relationships (it is called NETWORKING) that have followed me with several of my sites.

These "relationships" I built through commenting (with valuable and relevant information/questions) have helped me tremendously when "marketing" my site(s) because these other blog owners trust and respect my opinion.

This has led to me getting natural links from the front (and other) page of home improvement sites that get tens of thousands of visitors per month. My products are related to DIY and home improvement and these links are probably more valuable than thousands of blog comment dropped links (IMHO).

Of course, this is just my experience.

Blog comment is very useful for SEO in two ways...
1. If comment links are dofollow, it will help to improve PR of your site,
2. If links are nofollow and the blog is on high traffic, it may help you get refferel traffic from that blog

Any how, commenting on similar blogs it very good idea to bring traffic to your site, but the main thing is that comments must be genuine and not meant for posting link only, if so, no body would like to click on your link.