The idea sounds terrible to me. It will simply add to the flood of spam e-mail, and it will encourage the bigger players to abuse their mailing lists. (I still get About.com newsletters after repeated attempts to unsubscribe.) It will also debase AdSense as an advertising medium, because anything associated with spam will be a turnoff for readers.
This is a classic example of short-term thinking, not unlike the way Google released AdSense before it had quality controls in place.