I just flag every marketing email as spam. It's much more effective than unsubscribing since it tells your email provider to just redirect everything from them to spam, and it causes trouble for the sender.
Exactly. Unsubscribe is for newsletters you consciously subscribed to but no longer want. Anything unsolicited that isn't a genuine one to one communication is spam and all the "unsubscribe" option does is verify that your email is active and will be able to receive more spam.