I “borrowed” this idea from Jay Baer of Convince & Convert from a talk he gave at SocialFresh East 2012 this past week.
When someone wants to unsubscribe from your mailing list (or for member-based organizations – doesn’t renew their membership), do not allow them to say good-bye without offering a different way to stay connected. They are already leaving. You have nothing to lose. They may no longer be interested in your group emails but may want to stay connected through Twitter, for instance.
Don’t make communicating with them an all or nothing. Give them the option to connect in a way they will find more satisfying. The worst they can say is “no” and they are already doing that.