You need to work really hard in the beginning as a new blogger if you want to build a successful blog. I'm talking about more than just getting your site up and posting some articles because that happens everyday with new blogs popping up like a bag of Jiffy Pop Popcorn. You need to get out into the blogosphere and start interacting with other bloggers by leaving comments on posts. Don't just leave the standard "good post" comment because that doesn't really help you in any way. You need to leave good comments that can add value to the post you have just read and it's ok to disagree with someone as long as it's done in a professional tone.
I have learned that commenting can help you to build your credibility online and also generate new traffic to your site. Plus it can help add to your PageRank in the search engines which is what everyone likes. I really didn't buy into the commenting theory when I first started blogging because I was thinking that it would be time better spent working on my site and improving my online skills, but that is warped thinking now that I look back on it. I'm not telling you that you need to leave a novel sized comment on every post that you read on another site, but you want to start getting your name and blog out there for people to start seeing it.
Commenting is just another tool for you to use in building your blog and it really does have value for you. I don't ever leave a comment or link to someones post or their blog and expect anything from them in return. I do it because it is of value to my site readers and it would be nice if I get links and comments in return, but I don't sweat it because thats not my style.