It is not easy for Bounty managers to predict scam. It is better to talk to Bounty manager ad make a solution by which you can contact team of ICO , if it is scam then take help of bounty manager and raise voice against ICO team.
Indeed, I think it is still depends because there are times that the bounty managers who are to blame and sometimes the the developers. In my time in this forum I had witness those circumtances wherein the project is successful but the manager don't allocate the token and there's time that the developers itself are the scammers. It is difficult to determine but still it depends upon us on what will be our story whether to be fooled or to gain, so be fussy on the project where you wanted to participate.