At deviantart the top 5 weekly images are based solely on the number of favorites that were given to it. You want an image to be in the top 5, it's a direct reflection of your taste towards the image. People can go to your your favorites and see what kind of art you place in your favorites. I'm willing to bet that if it was ran like that here for the top 20, it would have different results because people couldn't hide behind anonymous voting. What eventually happens is the people with the biggest following usually get the top spots. People get the biggest following by being the best in their field. Sometimes one of the top 5 images is also from a rookie that happens to make a great image and it gets enough well deserved attention to put it on top. Yeah, sometimes people are also in the top because of nothing but popularity, but not all the time. Nothings perfect but it works better than this "you vote for me, I'll vote for you" routine.