Even everything above is followed correctly, still there's no guarantee that project will be good. However, if someone does enough research it's possible to avoid scam project. I am really bored on bounty and given up participating too.
There is absolutely nothing that can guarantee what the outcome of any bounty could be, even when the tasks are limited, with stakes counted promptly, it's still isn't enough of an indication that the bounty would end, but when bounties by certain managers, you can be rest assured that there is a better possibility of it being successful (or at least) pay it's participants.