Or when you think you've unsubscribed, multiple times, only to see there's a "Preferences" link on their unsubscribe page, where you find out you've unsubscribe

Or when you think you've unsubscribed, multiple times, only to see there's a "Preferences" link on their unsubscribe page, where you find out you've unsubscribed from 3 of the 48 categories of newsletters they send.