This will just make people post more garbage so they can qualify to have ads in their sigs IMO.
My thoughts exactly. It won't work...the more concentrated your posts, the slower your activity rate goes up - but that's not gonna stop the newbs from trying...
First of all, I agree with this change. Second, how would this not work? It's not like you can spam your way through activity levels.
You can. Simply open an (or 10) account(s), and spam as you usually would. (The spam is divided between the accounts so you can increase the activity of all of them efficiently.) Eventually (after about two months) you will qualify for most ads and will be able to spam the forum for pay.
My favorite solution in this thread is to require advertisers to only pay users who make large posts.
It may not get rid of spam completely, but it surely does reduce it a significant amount. The number of people who would do that are most likely less than the people who wouldn't bother. Either way, can't admins just IP ban?
EDIT: I also do not know what the best campaign setup would be. That's something that has to be thought into.
I think Theymos' solution is significantly better than doing nothing, don't get me wrong.