Yes bounty hunters Contributed the most when it comes to success of an ico, I'm pretty sure they introduce in more investors than rating site did. And about the dumping part i belive is just for the investors to blame someone
No, bounty hunters hardly contribute anything to an ICO, and that's why they get paid almost nothing. Frankly I don't know why they exist as most of them write empty posts devoid of anything intelligent, have fake Facebook friends and simply copy/paste information from the ICO website and call it a "blog." Then if a token should actually acquire value they immediately dump their stash onto the market.
Probably the most frustrating part is none of them are here to actually learn anything. They learned just enough to operate a wallet so they can get "free money." They don't contribute anything positive to the forum and make it appear is if its 90% advertisements.