EDIT: Well, on second thought, notice that in both cases, although pg stated the he thought downvotes should be used to express disagreement, more upvotes were given to other commentors that though downvotes should only be used to boo rudeness (which is my personal opinion, as well). So I think maybe there is a division in the community on how this is supposed to be done.

Actually, the experience I was just whining about is case in point for why some people think downvotes should only be used to boo rudeness. I think a lot of people downvoted me just because there was a response to me that was strongly worded, even though it was (in my opinion) not really even relevant.