I do not work for nor am I associated with Scoutmob.com.
I do however live in Atlanta, GA, and I have been enjoying Scoutmobs for a few years now around town.
When I use a Scoutmob, I consider it a test-run. I go try out a restaurant or coffee shop I've never been to before to see what they have to offer (food wise, service wise, etc.)
If I'm impressed, I'll go back. If I'm not impressed, well... at least you had a shot at keeping me as a customer.
On the business side of things, yes it will cost your business money. The purpose of a Scoutmob is not to make your business money - it is to bring people like me into your door, who would otherwise never step foot inside your establishment.
If you impress everyone who comes to your place with a Scoutmob, I guarantee some of them will come back. I can give you a dozen examples of this happening to myself. If I love a place, I will go back. Period.
I highly recommend Scoutmob - although the number of emails they send you a day is kind of annoying (upwards of 2-3).