The idea of site security and manipulation is a concern, but personally I don't even look at the rating thing for any images, including my own.
Not even sure what the purpose is or what it means for an artist.
I see lots of images in the "Top rated" section that IMO lack any skill or originality.
I'm not trying to make light of how seriously some people take the approval of others, but as most great artists died poor and unrecognised, perhaps a low rating (true or manipulated) should be seen as something desirable.