Your inability to be authoritative with the course of this service. Give the opportunity to btcjam users to ask for your assistance in case of any issues appearing between them. You are the judge, but you still don't know it, and the only one that can tell right from wrong with your service. Make people trust you by helping them, right now they seem to be shouting for your help, and don't give cheap excuses because you will dig your own hole. Bitcoin is the wild west and you should act like it, in your "house" you're the one making the rules.