I've noticed this for a while now and I think it is a bot (or an extremely immature person). In the last couple months, whatever/whoever is doing this just gives a 1 to every image in the latest images list at irregular intervals. The longer a screenshot stays in the current images list, the more 1 ratings it gets. I got four 1 ratings on my latest screenshot.
I think if it's possible, all previous 1-ratings should be removed and from now on only logged on users should be allowed to rate an image (or forced to comment when rating).
Otherwise, it's best not to have ratings at all (or "Top Ten"). It's useless when 10 people take the time to give an honest rating of an image, then some idiot/bot just trashes it without a thought.
On the other hand, the ratings mean nothing.
Ratings are an incentive for people to submit the best stuff they can and a way for people to reward someone who does great work. It also helps people find what others consider to be "the best".
When looking at a "top ten" list, people are looking for what others consider to be "the best" - not "some random average images that managed to escape having their ratings trashed".
