I would argue that the only infinite supply of deals are deals where the profit margin is so high that it supports profit at 50% off plus Groupons cut.
A restaurant does not have 300% profit margins, so long term a restaurant cannot support this model. Only service businesses, or businesses with fixed costs with low variable costs per additional customer, can be on there.
Restaurants have very high fixed costs and 60-70% margins (basically, the food) so even with a 50% cut to Groupon, they can usually make it work. With a 20-40% cut to Groupon, they can make it work without much deal overage or return customers.
