I see so the primarily utility of Groupon is that businesses can pay for a chance of repeat customers and/or extra spenders? I think the theater is a good example of the latter.

Then the question arises, why can't businesses do this themeselves? Why can't the breakfast place you frequent just advertise $20 worth of food for $10? Why Groupon? Is it because Groupon can send foot traffic on demand for a cut of the sales?