That IS the question. What is the protocol with comments? Should you ALWAYS leave a comment just to let them know you read their blog? Or do you only leave a comment if you have something interesting to say? Can you comment on old posts, or should you only leave a comment on the most recent?
Regardless of the protocol, I think the old addage "If you don't have anything nice to say, don't say it at all" fits. I was just looking at Red Tulip Photography blog. She is AMAZING when it comes to picture-taking. And there is a post called "A note from the photographer" and I am flabberghasted! Do people really need to be so mean? Look at her work! It is FABULOUS (did you see the pictures of the candy bars on her fam blog? Can you say YUMMY?)! Why do you have to say anything at all? Didn't anyone ever teach you manners? What is that saying - "It's better to keep your mouth shut and let people think you are a fool then to open your mouth and remove all doubt"?
And what about hate emails? What purpose do they serve? Does it really make you feel better? I enjoy a good rant as much as the next person, but come on! Keep people's feelings in mind! Grow up! That said, I love commments, just be nice...Just sayin'.