Bounty hunters have a great influence on success of the ICO campaigns, because this type of advertising catch the eye of potential investors, especially signatures on this forum.
I think in 2017, hunters influenced much more than now, at the moment, for the most part a lot of spam than advertising , I think that you need to do only quality advertising to projects received more funds in the ico
I believe that everything depends on the project / bounty of the campaign, the manager and the established rules. Because bounty campaigns can set strict rules, and the managers of these campaigns can strictly control spam and check fraudsters.