Actually Bloggers use no-follow for security for their site and they also use it for developing their site in competition. thanks.
Blog commenting is important to me. And it's helped me with link building. It just shouldn't be the only thing you do. But I have a hard time finding do follow blogs too. I usually googe niche+dofollow and someone has created a list.
Here is the link to install SEO for firefox: http://tools.seobook.com/firefox/seo-for-firefox-updated/ Just follow the instructions and within minutes you will have a set of useful tools to find follow and nofollow links. In my oppinion is very useful to have follow and nofollow links to your website. If you managed to have only dofollow links to your website, the google engine could suspect you are trying to manipulate the process and could kick your page out to the bottom of results pages.
Diversity is key - all dofollow links would not look very natural, just like only having links with your main keywords as anchor text doesn't look very natural. Having nofollow blog comment links with random names as the anchor text helps add a lot of diversity to your backlink portfolio. Plus, there ARE dofollow blogs out there, you just have to know how to find them. A few dofollow blog comment links on high PR edu sites can make quite a difference!
blog commenting is not useless if it is in no follow region. you can still get traffic from no follow links.
I would only use blog comments for buffering, unless they are of high quality (low OBL, high PR, and dofollow), but these are pretty difficult to find. You can search them using footprints. I fasten the process with Hrefer or scrapebox.
I think both things are necessary for each other, A visitor read the blog and take time then he write some text against the blog. In this way blogger can get the feedback easily and visitor can use back links to promote his site.
When commenting, focus on commenting on quality posts on high traffic blogs. While it might not count for much in terms of link value, a valuable comment can get you traffic and exposure, if you go about it smartly.
Blog commenting is very useful, whether follow or no-follow. In fact, a mix of both is very useful for Google to consider your site as getting backlinks the natural way.
Nofollow links are useful for getting direct traffic and I have done some testing and can say they are good for SERP too. So nofollow tag should not discourage you from commenting. Don't spam
https://addons.mozilla.org/en-US/firefox/addon/nodofollow/ you can use this.. but this not support at firefox 5 and 6
Commenting on the topic related to your site and check if it is still not a necessity for me. Bloggers want their blogs to read and they want interaction on your site through comments, but please do not abuse it. Spam is a really bad way to get backlinks and reputation is also on the line as with spam, you are carrying the site.