Just thinking loud , wouldn't it be better if those who give rating to the photos posted also give their comments on why they give it the rating.
IMO, rating doesn't help photog to inprove on their skills, but comments do. Personally, I would be please to see why my photos is good or bad, either way, it will improve me.
Also, I dont think that only the pros can rate it (just incase you get the wrong picture). Its just photog sharing their thoughts, that all .