A person who disagrees with everything anyone says. Instead of acting out and 'replying' this type of person marks one thumb down on a comment/UD word/failblog post in a hope to bury the victim in a negative trend of other people marking one thumb down because the first person did. These people are generally headstrong, or just don't read the comment at all.
prettygirl145 says: vid is terible. just bad. (5 thumbs down)
Johan87 says: I agree! s#!+ quality. (1 thumb up)
Prettygirl145 has been downthumb'd by a downthumber