Good point I think personal bias will always be there it is only natural.
At the moment there are over 1200 songs in the APRIL rock section impossible to listen to them all but I have had the same songs come up several times against other songs. I did check their position and they are all over the place. It would make more sense to ensure that ALL different songs were judged randomly until you have heard them all. What happens to the songs you have not heard.... and do all the songs get judged... are some left on the shelf virtually unlistened to. How many people on average judge and for how many rounds? The answer to these questions must relate to how fair the comp is.

http://www.soundclick.com/bands/songInfo.cfm?bandID=687727&songID=5238055