Bounty managers are not to be blamed only if they do contribute in the scam that is taking place and those ones are usually members of the team that launched the ICO at first place.
Even if you are not that implicated in the scam or you really didn't verify whether the ICO is a credible one by reading it's whitepaper , seeing whether they have an opportunity of making money and so on ..
I remember that lately a very known and trusted campaign manager have received numerous negative feed backs only because he knew that the campaign he is managing is a fraud , so the managers aren't really those to blame ..
Experienced enough bounty hunters can make the difference between a scam and the real deal and should alert people whenever they smell something fishy (which is already happening with a lot of ICOs ..) .