Comment Etiquette demands you:

Respond to almost every comment
Build relationships quickly and effectively.  This is probably the most important non-blogging blog job that a blog manager has.

Respond deeply
Don’t just say ‘me too’ or ‘yep’ when responding.  Show the commentor that you read and either agree or disagree with the comment.  If you’re going to take a minute to respond, you might as well take the time to make it a thoughtful comment.

Respond in a post
Occassionally take time to highlight a commentor or even a comment thread in a blog post.  Let your readers know that their comments DO influence your thought process.