The bad side of these bounty campaigns is that these people will get tokens and they can get rid of them for much less than the actual ICO's price with profit. That makes the price of the token decrease in the short term.. =/
But the other side of this equation is it is cheap advertising. Running campaigns reaches a much wider targeted audience than would be possible using adsense, facebook ads, or other platforms. I personally only join bounty campaigns that I am also an investor in, or plan to be. That way I increase my holdings and help spread the word.