If you are referring to the services being a scam then, try to find a bounty running by TokenMarket, BountyPortal or reputable bounty managers on the forums but If you're speaking about the members impersonating other members then there isn't much that can be done here. If the manager is vigilant, that shouldn't affect the original participant in anyway.
I agree to this. In addition, you could also try to research on the project first before joining bounty campaigns. This will help you to know on whether or not the campaign is a scam. Also try on reporting the members who may be abusive for them to have a red trust.