As a service provider, if I could "buy" a satisfied customer (That means repeat business for the next, say, ten years.) and the "cost" of that customer is 50% off my first job, I'd take it in a heartbeat! If my average bill is $100 and I am going to get ten of those over time, I am earning a little less than $1,000. (considering net present value) However, I just got a new customer. That is worth something in opportunity cost.
If this person becomes a satisfied customer and tells five of their friends,there is no better marketing! And all this for $50!
This is why lawyers and accountants often give the first hour for free.
On the other hand, if I offered my services on Groupon and end up with 500 responses, I could not begin to handle the response. How do I vet 500 possible new clients quickly? Exactly the reason I don't advertise on the web. (nor in the LA Times)
I suspect that most brick and mortar businesses would have the same response. They just don't know how it will work nor if they can deal with it if it does work.
This is why internet startups are and will continue to be a fast growing business. Most small businesses haven't even begun to use the internet as it can be used to decrease costs and increase efficiency.