I will try discribe below what I found:
1) Bounty cheater with multiple account:
2) Scam ICO:
3) Corrupted manager:
4) Immature manager:
5) Unlimited participant:
Solution: It's very hard to find solution. But I think it's not impossible. First try to find multiple account holder and report to managers. So that many participant will be disqualify. Before participate any bounty do your best research what can you do. And share your opinion with others by reply on thread or ANN.
Managers should minimum research about ICO before start. If they exit scam that's is different case. But before start should little bit research what you feel. Don't be selfish. And you can limited participant for bounty to get quality promotion.
For participant try to choose best and reputed managers in order to get good payment. Avoid immature managers.
I just share my thought. If you have more idea it will be much appriceated to share here.
I think the best solution is our responsibility as bounty hunters - do research. We are responsible to know what we are getting into and hence we must scrutinize the bounty campaign prior engaging with them.
The best solution is preventive and not corrective. ICO scammers are becoming successful because of irresponsible bounty hunters. If we will become responsible (doing our part by researching the bounty campaign before joining, prevent ourselves by being ignorant) then ICO scammers will be lessen and will not be tolerated.