Right now predictit is a negative sum game because of the need for fees to keep the site running.
I have previously suggested predictit.org implement a scoring mechanism that would rate the trades of players with an eye of showing players that are consistently good rather than just lucky.
Once such a mechanism exists, there could be room for small prizes given the best players. That would create some real recognition for trades that goes beyond the returns on bets and make the whole game much more interesting.
predictit.org is not yet a viable "investment" because of the high fees involved. What predictit.org does function as right now is a sound test of political intuition. I think by giving real recognition to th at predictit. can increase interest in the site and trading volume.
This is particlarly important in "thin" markets where there isn't that much trading volume yet,but there potentially might be.