I disagree, if someone likes a restaurant then they're likely to come back even if they can get a cheaper meal elsewhere, price isn't the primary factor most people use in choosing a restaurant.
Partly - but people who like trying new restaurants are going to keep trying new ones. Not stop because they found somewhere they like. They might like the next place even more - and at half the price I'm sure they will.
As someone else noted the sample is very small, likely to only cover a dozen restaurants, so were talking about 6-7 places that wouldn't use it again. Also if you look at the comments made by the restaurants a lot were complaining about fraud (people photocopying groupons) and low tipping rather than lack of repeat customers (although there are a few along those lines as well).
According to the article, less than 32% of the customers visited once.
"The 32% that said they didn’t make a profit from the program reported that customers rarely bought more than the coupon deal and few returned to the business at a later date."
If over 68% of the customers returned, then I'd call that a huge success.
