Re: Terrible business model
I definitely think restaurants who use the service are insane or desperate. It's basically a terrible loan - sell a huge quantity of vouchers promising to serve the same food for 50% of the list price and then Groupon will give back 50% again of that on some schedule. Strangely enough lots of restaurants who do this go out of business soon after because the cheapskates have moved onto the next offer.
A far better strategy for any restaurant is to produce a set menu (e.g 3 courses for £15) and write that offer up on a big sign plonked outside. The restaurant keeps all the money and can deliver better food which makes for happier, repeat customers.