I have a question for you (I'd appreciate it if you'd take a few seconds to drop by an leave your answer in the comments): do you read the comments on blogs? Do you only read them when you're considering posting a comment yourself? If you've left a comment, do you go back to engage in the conversation, or just have your say and leave it at that?
Okay, that was three questions. Nobody's perfect.
My questions were inspired by something Demian Farnworth wrote over at Copyblogger:
If you want to influence people, leave thought-provoking comments. Share additional information [other people's articles, videos] that builds on their existing work.
And ALWAYS ask questions.
Online influencers lead the conversation with questions.
Good advice. If you ask questions in your comments, I'd imagine the odds of getting a response from the author of the post (even if few readers read comments) go up dramatically vs. just leaving a comment. Not all bloggers habitually respond to comments, but a comment that includes a "call to action" (a.k.a. question) may get treated differently.