Thanks for the feedback! A dislike button could be introduced as well of course... It's the idea I want to get out.
You are right on the abuse part, but this problem is unavoidable and exists for all sites out there. I also don't think this would be too much of a problem as we could balance it with the "upvote" votes (i.e., make "upvotes" have a stronger impact for trending). The idea is to combine both systems to get the best of both worlds
Voice has gone a long way to try and mitigate it.