I don't have any additional ideas to say something different from the others, but the most obvious impact of having forum without signature campaign is a drop in traffic. I think signature campaign are forum's way of rewarding the majority of its contributors, but in the end some managers may choose lot of posters who don't really care about the quality of their posts which then becomes a problem.

Some managers care deeply about suggested signature campaign guidelines, some may not, and the worst are signature campaigns that pay participants in tokens or coins form project under development. You can differentiate the quality between participants paid in bitcoin and participants paid in token/coin, most of them are never the same. I agree that many campaigns that pay their participants in bitcoin are required to post something of high quality even if there are many participants who may have lower quality posts.