There was a chaos in yobit.net signature campaign as far as I can remember but were they banned here? I can't remember.
Has it ever happened that due to spamming, theymos banned any signature?
Good question.
It is not always company advertising some service that should be blamed for spamming in forum, in some cases campaign managers should be temp-banned for accepting spammers in their campaigns.
They are not only hurting service they are working with but they are making all other bitcointalk forum members look bad.