I'm tired of merchants complaining about Groupon promotions that fail. It's your responsibility to do what's right for your business.
Groupon is a fairly complex promotion, and the best way to use it isn't really that obvious. Also, groupon has limited itself to the specific promotion that is most profitable for themselves. (You could imagine that in an alternate world they might want to expand to a broader set of offerings.)
Although, I have no intuition for what percent of Groupon's revenue comes from customers in which groupon is taking the entire surplus, half the surplus, etc