I don't think we should ever remove signatures from everyone all-together though as it's not fair that spammers will ruin it for everyone else and those will be the people that will immediately leave this board to never return if that happens.
Agree. This forum would become a ghost town overnight if signatures were removed, and I don't think anyone here wants a solution that drastic.
I believe in second chances for the most part, but it worries me what kind of precedent would be set if people started getting lesser consequences for plagiarism or second chances based on rank. Theymos is right, though. Every case should be judged according to the circumstances and context, but that's assuming we really know what the facts are, and you can't really rely on the person who got banned to be completely truthful.
Roger Ver would be the first to capitalize on signatures being removed. He would start tweeting all day about how his forum allows signature campaigns and he would get all the traffic in there, which in return he would not only get more money due ad revenue but the increased traffic would rank his forum above bitcointalk.org on Google search results.
Some people are too idealistic and don't understand internet marketing and SEO in general. Keep the traffic source and improve moderation is the way to go.