I said this in another thread before, the problem with pretty much any voting system is that it relies on fair ratings and human decency, I don't think I've seen so much concentrated dishonesty in one place before and it puts a damper on the game jam.
As you said, I've noticed plenty of 1 minute ratings, copy paste spamming every rate thread, comments that make no sense to the game I've just played and people lying about reviewing a game just to try and trick as many people as possible into playing their game.
This is my first game jam and I've quickly learned that I'd rather have 20 people rate and get some good feedback about how I can improve as a developer as oppose to 40 rates that just say 'rated'