It's all depends we choosing a project.. If you want a good quality bounty, just follow the most trusted bounty manager, find project who have a strict rules for participant (strict rules have possibility to avoid who cheat on bounty).
I suggest you think again when you believe too much about them, because it is simply not possible for them to be so good without profit. But anyway this is the good way that I see from your comment and You should be more careful with yourself.