Most people thumbs down when they disagree with an answer
It other section there are often people who gives inaccurate answer, so thumbs down indicate that the answer may not be accurate, true or actually answers the question.
And many answers that get alot of thumbs up are actually good answers, depeding on which section we are talking about. Here P&S, most funny, sarcastic and witty one liner gets alot of thumbs up
I do that alot too, I thumbs up any answer that makes me laugh