Consider this:
A restaurant collects approximately 20 business cards a day by giving away a free sandwich once a week. Most of those business cards have an email address written on them.

In 2 months that restaurant will collect 800 business cards. Parkville Designs can create an email with a picture of a juicy mouth-watering hamburger and a coupon for $1 off. That email would then be delivered to those customers around 10AM on Friday, just two hours before hunger strikes.

Assume on that same Friday, 40 new customers redeem their e-coupon. If the average bill of those customers is around $20 (figuring that most of the coupon users brought a friend) the restaurant owners have just increased their gross sales by $800 ~ Worth a try?