<brain explodes>
I can't wait until mailing lists try this: "To unsubscribe from our list, please send email every 24 hours to keepunsubscribingme@___.com. Here's a webapp to join to simplify the process." or "Would you like Sears to stop sending these coupons to your house? Please send a postcard to ___ every 30 days." Lol.
(Not saying this is a bad idea. What do I know? I'm going to keep it on my radar.)