Eventually the account farmers will run out of merits to tip themselves. Hilariousandco has nailed a few accounts already for merit abuse, as has Lauda I believe. This is when we can successfully implement rules for campaigns(or theymos cam implement them).
Something like users must earn 5 merits a months for their account to display a signature if being done by theymos or managers can make a user earn 1 merit per week to stay in a campaign.
The problem is still gonna be the same managers whom accept anyone and everyone. If all aren't on board it will fail. Kinda why I feel theymos should implement the restrictions.
Making rules for campaigns to follow means that someone has to police them so my suggestion pretty much amounts to the same thing but automated.
As to the numbers, I suggested 1 Merit / 2 months, but really if it's 5 Merit / Month or whatever, that's just detail that needs to be finessed.
I like the basis of the idear, however i do think there are a couple high-ranking members that post only very seldomly... If they have only made 1 or 2 posts since the merit system was introduced, they risk losing their sigspace if this system were to be automated. Granted, those members aren't in a sigcampaign to begin with, but they do use their sigspace to promote threads, promote their own businesses, insert funny quotes, show the address of their tipjar,...
I guess it might be better if mods had the power to disable signatures for everybody who received less than 1 merit in the last month... That way the mod could use his own judgement wether or not the person in question is a spammer, or just a very low volume poster that just didn't receive any merits because of their low post frequency.
Just my personal opinion tough...
There is inevitably a little collateral damage as you suggest. My thinking is that a signature is a reward for providing content for the forum, so if you no longer provide content why should you continue to be rewarded in perpetuity?
I don't think that it would solve the problem. The spammers would just send themselves (or buy) one merit point every two months.
Maybe if somebody received a large amount of demerits they could have their signature rights revoked, or maybe an increased cooldown between posts.
They'll soon run out of sMerit. Demerit is open to hundreds of times the level of abuse.