1. Escrow the bounty funds and make sure it's managed by trusted managers.
2. Never join any non-escrowed bounties if you fear the bounty won't paid you in the future.
Those 2 suggestions I provide above 100% will prevent from bounty scam and make bounty scam will go away since no one is interested.
Even if the stakes are escrowed and you received your shares, that does not mean that you are going to make a profit, the coin or token need to be listed in the exchange and there should be liquidity for you to cash out your coins, unfortunately, so many coins coming from bounty failed to get in the market and get a good value, I have experienced that when I am very active in bounty.