If Bitcoin network fees get higher than shipping costs, it would make sense to start giving participants physical goods for their signature campaign participation. I think it would be cool and probably help cut down on abuse if people had to give their mailing address to be a part of the campaign. Maybe try shipping some silver?
This would only be viable if the campaigns were limited to users from a certain country, in this case we have people from all over the world in subscription campaigns...
I also think there are a lot of people here who prefer to remain completely anonymous.