Lets say they put a pay per post of 0.0015 (more than last time) on the bitcoin protocol section, suddenly everyone will post stuff that doesn't make sense there.
Which is why campaigns should select individuals as they apply (only the best posters are accepted to ensure their posting habits remain the same - that of quality)
The selection will never be perfect in a campaign with 100's of members and 50 BTC budget.
Also sometimes people change their posting habits after join a campaign, and accounts might change ownership