What did you learn in altcoins, those projects didn't paid bounty hunters even after successful. We can gather information by all unpaid bounties and with reasons why didn't paid. For us this is very hard when our good research is successful but admin cheated to bounty hunters. List why didn't paid, your experience and history about unpaid projects
I am not so sure if this will really help to isolate those project owners who have done this kind of cheating as we don't have the power to stop them. But this kind of scenario is only part for us as a bounty hunter therefore we really need to be wise on whom we would like to support so our hard work and time will not be wasted in the end.
Most of the successful projects will release the bounty rewards and if there are owners who didn't give the bounty rewards will likely a scammer and it is very rare for a scammer to become successful. I haven't experience this kind of scenario yet as I always double check everything before following any project, so what I can say to all the bounty hunters is to become vigilant in every bounty campaign that you would like to join.