I believe most people participate in multiple bounties at a time because bounties are no more profitable so if you do few, your reward too will be small. If you participate in many and some of them turn into scam, at least you will still make some dollars from the remaining.
I think in such cases, the bounty hunters take the campaign just at random.If they're lucky,they'll earn something.I think you just need to pay more attention to the choice.Spend more time researching campaigns.Choose the one you're sure of.