I agree it's getting rather annoying, even if they aren't banned all together it's very easy to put limitations on signatures I think that signatures shouldn't be bright colors or anything above 14pt. Obviously, this is my opinion but, I think they are good limitations which would keep the advertisers happy and the business which is using people to advertise. Though, I hope they do get banned from advertising.
I have participated in a ad campaign a few times, however I had to reconsider advertising for a business which promotes spam and useless posts, especially with one of the businesses offering double the amount of posts for double the money now. I think something needs to be done otherwise, we are going to continue to see increase of spam. I have added my first person to my ignore list and I think he'll be on a lot of peoples ignore list as he is probably the most famous spammer on the forum right now. Most of his posts are useless and have repeated what someone has already said and he continues to do so every day. I always see his username posted in one section where he has replied to 5 or more topics where he didn't need to contribute to but, felt the need to earn a little extra. There was discussion a few months ago that his type of spam is acceptable and the staff members talked and said that it is only just acceptable.
I'm going to be adding a few more people to the ignore list too soon which I hate doing too much because I can't read half the topics because no doubt that the people I ignore nearly post in every single topic there is on this forum.
I think it's a great idea, paid signatures add nothing to the site and only encourage useless posts. There are way too many people who post in every topic because it gets their post count up, the posts look useful but overall it really just adds to the noise.
Good luck getting glorious leader to make a change!
Edit: Maybe, I should inform people running the campaigns like Stunna about the people who are spamming useless posts or generally annoying replies and maybe he will remove them from the campaign.