voted no because:
You can already report it to the staff via the link and/or report it directly to the campaign manager.
But many people dont know about that, But when they see a link in the signature about report abuse and they are redirected to a link where they can post, i think they will surely do that.
I don't think so. most of them are probably new users who doesn't know the forum very well.
and I think 70% of the reports will come from users that doesn't like signature campaigns in the first place, making their decisions biased.