Or, a signature campaign will need an approval before running one, plus, a fee to the forum for running the advertisement. (you don't get anything from the current campaigns, right?)
I've thought about Signature Campaign Managers/Runners having to pay to a small fee to the forum before they can run one, though finding an appropriate price could be problematic. The forum doesn't gain any monetary value directly, though the number of users/traffic signature campaigns bring in will obviously be quite valuable/significant.
Why don't you (or: whoever feels responsible) start up a poll as the new forum software comes
closer? I guess that a big majority would be in favor of disabling signature advertising alltogether.
Polls like this can be easily manipulated by multiple alt accounts or account farmers especially when they have money on the line.
Cross posting my post from where BadBear originally posted it:
Sounds like a great idea and compromise. It has my support. How about an 'ignore this user's signature' button in a similar way you can ignore users? Or maybe certain staff or admins could have the choice of disabling certain user's signatures as punishment instead of a ban. The option to either disable them for a short period of a week or something or for three-time offenders disabling them forever (or something extreme like several months even up to a year) may be a greater deterrent.