You are right once again, the forums doesn't gain money by allowing advertising signatures, but we aren't really about profits here. The general policy here is to only ban the things that cause issues that can't be fixed, rather than banning paid advertising signatures, we would rather to help fix the issues they cause and continue allowing them, because from the user's point of view, its pretty cool to be able to post regularly and make some bitcoins. The problem is the spam created when it goes beyond just posting regularly.. We all acknowledge that paid advertising signatures promote spam, and we have been discussing ways to limit this for a while now. Freedom of speech includes freedom to promote whoever you want, for financial motivations or not. We are trying to figure out ways not to limit/censor the users here, but put tighter restrictions that hold campaign managers more responsible to reduce spam.

*edit*
The only way I see to remove the incentives for things we don't want to happen, would be to remove the marketplace section all together. There would probably still be paid advertising signatures, and also account trading for that reason.

Personally, I see paid advertising signatures as a reason to legitimize account selling. What could only be useful for scamming before, can now be used to make an honest buck with paid advertising signatures. The spam created is another issue, and thats where we will start.