Too many participants ? I must disagree with you , we are no yet on the mainstream of bounties , ICO's and so on. After we gonna reach this stage , we are gonna see some really awesome bounty programs with a lot of participants in all the bounties.
This is for the reason that they do not think of the benefits that the participants will get rather than their own benefits. More people joining the campaign would create and attract more investors and more profit will be generated. There is no solution of this problem because every body want to earn the money and no body stop to it.