The idea is that people will give a THUMBS UP vote for good responses that help whatever the topic is. If the response is NOT helpful and does not help or contribute to the Question/Discussion, it should get a THUMBS DOWN. If a post has 30 UP votes and 10 BAD votes, their "score" is a 20 (30 - 10).
Of course when we get 100s of people voting, we will then easily be able to see what the "Best" and "Worst" answers are, which are very valuable.
Members that get a lot of THUMBS UP votes are obviously doing a good job, so we will reward them. Members that have DOWN votes are not doing a great job, so they shouldn't be rewarded.
Does that make sense?
Sources