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.
Bounty hunters can sell tokens earned for the bounty and buy some new token on the exchange. I think it's better to buy a token after listing it on exchanges. Purchasing tokens of preacts that are at an early stage is almost the same as participating in ICO.