IMHO, the voting system allows a thread to stay smaller, lighter and cleaner.
Instead of a thread full of +1 or "yes, I agree" or similar post, people who agree with a popular post can just click the +1 button to add their input with out cluttering up the thread.
And a similar comment would go along with the "-1" button. If you disagree with someone's comments, but aren't so enraged with it that you need to write a paragraph about why that person's opinion is completely wrong and why they are an idiot, the "-1" button provided some politically correct grey area.
I fully realize that the purpose of this, or any forum is to get people to post an opinion or share something, but the reality of many topics is that a lot of forum members don't really have an earth shattering comment worth posting.
IMHO, the voting system, both positive and negative, is a wonderful way of keeping threads free of "me too" posts, or at least limiting them.
Its a shame that a few vocal members got the negative votes removed. On several other forum's I frequent, the positive/negative voting system works great, and at least in my mind, provides a "stop and think before I post this controversial item" means for people who might just otherwise post stuff to stir people up.
Just my opinion.