What does it matter how big a portion agrees? It's not like the forum is representative of the player base (as only a tiny fraction of players hang out here and I bet you that they have different opinions from the general player base), so it's not really information that can be used reliably for polling or anything.
To me it is a simple way to see of how big portion of people in the forums think about the issue/post/idea. And if a post about "the game will bomb if thing X isn't fixed/added" is disagreed by 90% of the few hundered voters, I think that we can be fairly well rest assured that we are not going to see a flood of bad reviews once the game comes out, even if those disagreeing are just by us here in the forums.
You know that the old forum didn't have agree/disagree buttons right? And it was never a clusterfuck of such posts. People that had nothing to add but "agree/disagree" most of the time just didn't post (*), which is exactly right as such comments don't add anything. I don't know about you, but I don't really care who (or how many) agrees with what - what matters to me is the "what", i.e. the ideas and arguments themselves.
(*) There was the occasional "+1" posts but it was perfectly manageable.
I'm glad to hear that such thing hasn't been an issue. I wasn't around here back then.
I care about it, mostly out of curiosity. To me, it is a harmless way to see statistics about people's opinions without the need of creating polls. It doesn't harm the discussion but for those who are interested, can give an idea of how people think about it.