If we start banning campaigns and their participants which are largely spamming, future campaigns will very quickly learn to employ a manager who actually pays attention to post quality.
And they should, you cannot simply start a campaign and employ just anybody to run it, neglecting one of the most important role the CM plays in the campaign by checkmating users posts quality, and only top managers do that.
Other campaign managers should either try to improve on how they do their job, making their campaign participants pay more attention to what they write that gets them paid. Or the campaigns should only choose the very best managers in the forum.
As for the BTC rate, I think every campaign would pay it's participants based on the effect the advertisement is having on their company, if they are actually getting traffic, they wouldn't mind paying a little more than others, I doubt if the forum can impose anything on them.