I cannot comment on blogs at work, so to the extent I do comment, it’s after work hours or a day off (or, perhaps, during lunch or a break).
You know what that means? Sometimes the conversation is over at that point. My point has been made by someone else, and I’m not a “me, too” fan, not to mention that reading and finding those blogs to comment on cuts into my limited time to do my own blogging and reading (and other real life things.)
I only comment when I feel particularly compelled or if I think I might have something unique to add. If someone has already made my point, I don’t comment to agree or say I feel the same, and people have often already made my point because I don’t usually have time to check blogs every day so I tend to be several days behind.
I certainly respect people who are better or more regular commenters, it’s just not who I am or how I interact with the blogosphere. I hope people know, though, that just because I’m not a prolific commenter, that does not mean I do not enjoy or find valuable the content on my favorite blogs.