It is not right to blame bounty managers,  since it is you who decided to participate in a certain bounty. You have all the rights to refuse and not participate in it yet you choose to be in.  Bounty managers have responsibility also,  so as you.  At the end of the day it was your decision that leads you to being scammed. But then,  you don't have to feel discouraged. Go on and you will definitely find more bounties that are great.