I can say 100% that 60% of all bounty is a Scam. The reward for them is either given and the tokens will lie on your wallet forever or do not give at all. Then what's the point of doing this ?
Simplest decision for you, if you afraid of scam, will be to connect to bounty campaigns when project already raised softcap. Yes you will get not a full income, but you will more sure in choosen project and will get your tokens faster.