Icos look for bounty hunters to promote their project through the power of social media.Sometimes, some of these hunters also double as ico investors. But it looks like bounty hunters understand ICOs project and are able to determine very good projects before they invest because of their experiences in different projects.
Yes, us bounty hunters, most of the time eventually become ICO participants as well.
It's a strategy as well to lower the total cost of purchase of ICO tokens since the bounty will lower the price entry.