Poll: Why do you comment?

I've noticed two tendencies with my own comments. I either comment to 1) get up-voted, 2) have my position or thoughts critiqued, or 3) to critique/commend another comment. I very rarely comment with the motivation to further the discussion (which I why I think we should post comments in the first place). Perhaps that's just a commentary on myself; perhaps not. What is your most common motivation?