Maybe a decline in account farmers would also mean a decreased payout for signature campaigns, or even fewer campaigns in general - which would probably be good.
I doubt if that would be the case. If there is a decline in account farmers, my guess is that you would have signature campaigns paying higher for the remaining participants. Sites would anyway discount alt traffic when they take into account whether they want to advertise here or not.
I agree with botany, campaign owners will be willing to increase pay to make active campaigners to switch to another campaign because of the higher pay and with higher pay, this would also force the campaigners to make sure their posts meets the quality standards to avoid being kicked out of the campaign or posts not being counted.
Well, in either case then the result would only be positive for the community as a whole. It would be best to remove the account farmers and add units of evil to their IPs. This would also affect the account-trading market - the farmed accounts that were sold would also be banned and thus a slew of others would fall as well. Now unfortunately, there is no way to prove that you were sold an account due to the fact that one could simply sign a message indicating a past date for the trading of an account.
Could it ever be possible to sort of "nuke" a non-newbie's posts, but keep them unbanned? (Or have something where if all of your posts are in Games & Rounds, you gain no activity) This would harm account farmers and keep the main accounts of those who bought accounts safe. I'm purely thinking of ways to impact only the worst offenders, though I don't condone account trading either.