Personally I think there would be a phase without Signature Campaigns to see how it could improve the spamming occurrence in the forum and then after the hype is settled, it get's back in the forum.
I agree with SFR10.
theymos should at first, test out the consequence of disabling signatures for a couple of months.
Then with few iterations he can slowly start enabling it for the betterment of community as well as for the newly emerging Bitcoin-related websites.
Adding a "spam-meter" would also help in preventing obvious spams that are generally done by members nowadays in order to reach his highest post count.