Everyone whoever got up to the Bronze star knows that the SiftCrack is the want to gain stars, TOP15 videos and so on. The Web 2.0 equivalent of leveling up in World Of Warcraft.

 I think this can be extended further by introducing SiftCrack, a recursive element that pushes Sifter participation by statistical comparison taking the gameplay element of sifting to another level by encoruaging participation. 

 Think along the lines of Siftbot becoming a full avatar and pushing the meatbags to perform better. Like he would be a lil' icon on the side that would post statistical messages based on your last post performance.

 "Your puny video fared better then your last miserable attempt" 

 "Your video broke Top 15 and has the 2nd highest votes of all time!"

 "Your comment got upvoted by 6 meatbags who should really get out more!"

 Anyone who played Teamfortress 2 and seen the nudging that the game gives via statistics would instantly know what am talking about.