Bounty hunters help to expose ICOs to crypto related audience to attract investors for the project. No matter how promising the project may be, if the ICO fails, the project won't see the light of the day. Bounty hunters are very important in ICOs. But there is one thing am not happy about bounty hunters. They usually dump their coins at any price the moment it is listed on an exchage which usually drops the price of the coin even below the ICO price putting the investors at a disadvantage. I want to advise the hunters to hold their bounty tokens for a while in order to maintain a good price for the coin. We shouldn't forget we are all stakeholders
I think bounty hunters earn their cards through labor and they have the right to choose the time of sale. If you do not want your hunters to sell their cards you should offer a great and potential project then they will retain, or you can simply pay them ETH or BTC.