We believe you should only get the mail you want to get. Some of you already use the "Report Spam" button on all kinds of unwanted email, and for that we're very thankful: the more spam you mark, the better our system gets at weeding out junk mail.
Unsubscribing from mailing lists and newsletters you subscribed to a while back but no longer want to receive should be just as easy. Searching through individual messages for little unsubscribe links is too big a pain —you should be able to unsubscribe with a single click.
So we just launched something that makes this all work better, both for Gmail users and big email senders. Now, when you report spam on a legitimate newsletter or mailing list, we'll help you unsubscribe. After clicking report spam, you'll see a little dialog like this
Official Gmail Blog: Unsubscribing made easy