This effect has been confirmed empirically by a team of marketing researchers who tracked three businesses for a year after they offered a social coupon. All three companies lost money the month they offered the coupon and will have difficulty earning it back. According to analysis done by the two researchers,
V. Kumar and Bharath Rajan, the companies would need 15, 18, and 98 months (almost eight years) to earn back their lost profits. The reason? “The three businesses had difficulty retaining most of the new customers who were attracted to the coupon offers,” the two researchers wrote in the MIT Sloan Management Review.

via Why Groupon and Living Social Are Doomed – The Daily Beast.