However: the forum will never intermediate these transactions. We will not touch the money involved or perform any sort of "screening", etc. Also, I have no particular desire for the forum to take a cut of sig-ad transactions.
This is a shame. While I understand you don't want the liability, I think it would be a boon to the forum's revenue and could be a cool way to reward users here.
If signature advertisements were as simple as clicking a box in your profile settings to activate it once you've reached the designated member level, and you received payouts based on views/clicks, that would be a pretty cool system. No more signature campaign managers. No more favoritism to alt accounts. No more war on newbie accounts. No more shit-posting.
I second this. I have no idea how much work it would be to integrate this into the current forum software but it sounds like a solid idea to weed out all of the low quality posts.