It seems that commenting on other blogs is a way to get yourself noticed in a few ways:

1. It gets you a link from another site to your site raising your value in search engines. 2. It gets the author of the entry to check out your site. 3. If the comment is intelligent, someone reading the comments might actually click through to your site.

Since these are all true and if you are after traffic to your own site, it doesn't seem too altruistic or selfless. no? yes?

I'd think that an owner of a blog would prefer that someone else comments on the entry on the commentor's own blog. This way all of the benefits that I described before would benefit the blogger that wrote the original entry.