I believe that commenting on other peoples blogs is very good for your own blog. For example:
1. It leads blog readers to your blog.
If you make a serious comment most likely some of the readers will pay a visit to your blog.
2. It makes the blog owner notice your blog(some exceptions)
For example when I get a comment I tend to check out the commenter’s blog and read a few posts.
3. It can start an online friendship that leads to back/forth linking.
Got most of my links/blogger friends simply commenting 
How does this affect your blog? More direct readers, and indirectly with time might increase your search engine ranking, plus you might make some new friends.
rowdyruby said,
February 13, 2008 at 12:24 am
I agree! I know I have a lot of lurkers on my blog and it would be so nice if they would take a few seconds to just say hello, you know? I’m a friendly person and I like interacting, but since I made the leap from LiveJournal to my own domain last fall, I get barely any bones tossed my way.
Anyway, my name is Erin and I found you on the BOTB! I’m over at http://ohhonestlyerin.com
Ragnar said,
February 13, 2008 at 10:56 am
Yeah i know how you feel, I did a checkup on my incoming links yesterday and noticed blogs having me in their blogroll that I’ve never seen before. Personally I’d be glad to visit all the blogs my readers own.
Michele said,
February 13, 2008 at 11:14 am
I enjoy leaving comments
BTW: Heya!
~Michele of
http://michelefamily.wordpress.com/
This Mom said,
February 13, 2008 at 3:00 pm
I have a lot of lurkers to my site, and very few commenters. I chalk that up to me being a boring and/or bad writer.. LOL
I try to comment on most of the blogs in my Google Reader each day, but my list is growing so long its hard to do.
Found you through Blog Explosion… nice site!
Ragnar said,
February 13, 2008 at 5:21 pm
Michele: Same here but only if i feel like i can make a good one
This mom: Lol yeah same here, then i did a incoming link search found several posts/links to my site with positive comments, so i figured i must be doing something right.
usedtobeme said,
February 13, 2008 at 9:36 pm
I agree but I’m a sucky commenter. I lurk at a WHOLE BUNCH of sites. I need to work on my commenting skills.
PS nice to meet you. I came via Blogexplosion
Wally said,
February 14, 2008 at 12:44 am
You got my Battle of the Blogs vote
Andy said,
February 14, 2008 at 1:12 am
Commenting is definitely a key to building your own online relationships and expanding readership.
I try to visit and comment on the sites of all my visitors. I’ve even begun offering links for all the relevant comments on my blog.
Siteunseen said,
February 17, 2008 at 7:24 am
I agree with everything you’ve said. I’m a commenter. I figure I wanna know when people are reading my blog; of course they want to know if we’re reading theirs too .
Chaim said,
February 19, 2008 at 9:33 am
I have found that commenting on other blogs is the very best way to attract readers to your blogs. The ratio of quality hits per comment is much greater than any sort of ratio generated by traffic building sites, (a gimmick which I abandoned quite a while ago).