Bounty restrictions can fix few problems facing project price drop after listed on exchange,
1) if any dev want to avoid dumpers then they must limit bounty participants, the limit the participants they better ,if a bounty only request 300 participants at highest and the 300 became a dumper it won't hurt ,unlike 2000+ participants
2) devs should forget bounty when still on ICO ,allow bounties after your project finished ICO successfully and make your project is doing great before allowing bounty
This are just ideas ,if you have anything better please drop on here and let's share.
Sorry, but you are completely clueless about who is doing the dumping. It is not bounty participants who represent 1 to 2 percent of the tokens. It is people who bought tokens at a discount in the Pre and Private sale. You see companies offering discounts as high as 90% off the ICO price and no holding period restriction on people who buy during the private sale or presale. There are people who make their money by doing nothing except buy early at huge discounts and then dump as soon as it lists.