Now I'm not stupid and I don't try to unsubscribe from newsletters I didn't request.
But, have you ever noticed, that even with legitimate newsletters the unsubscribe process is shady? When you subscribe it usually takes about 5 seconds before you get a welcome e-mail and your first newsletter. When you unsubscribe you get a message that you will be removed from the mailing list in 10 days or some other ridiculously long time frame.