Guy walks into a restaurant, asks the waitress "How much is the meatloaf?"
"Fifteen dollars," she says.
"Too much. Will you take $10? No? How about $12?"
Couple of years ago, the guy would have been thrown out. Dude, a restaurant's not a garage sale. You don't "negotiate" at the grocery store or the corner cafe. Or do you?
Restaurant coupons in general, Groupon in particular, are little more than one-sided negotiations, discounting the menu by half or more. How much better (for the restaurant) if the owner remains in control, explaining to the guests that tonight, yes, there's one "chef's special" (something that's not on the menu, made specially for this evening) and another "weekly special" (something that is on the menu but whose price is discounted).
I hear from a stream of restaurant owners who complain about the lack of customers but their response is precisely the wrong one: hire an outside marketing company, cut prices and cross fingers. Instead, it makes sense to stay in control.
Downtown,, Blueacre Seafood sends out an email every day to its followers and fans. Every day an informative email, every day a different special. Teressa Davis does this because she and her husband, Kevin, own the restaurant (as well as Steelhead Diner in the Pike Place Market). She shares my abhorence of give-away-the-store promotions.
For example, when it came time for Mondello Ristorante in Magnolia to celebrate its seventh anniversary, I recommended to owner Corino Bonjrada that he create a $7 birthday menu. Not the whole menu, but two appetizers and three pastas, plus a $7 glass of premium wine. The offer was emailed to his list of loyal customers. Mondello doesn't lose money even if every visitor to the restaurant for a week orders nothing but the $7 items (though you know that's not going to happen), but Bonjrada brings in more guests and creates good will besides.
The one thing that I'd add to in-house promotions like this: require (or at least request) that the participant provide (or confirm) an email address. They're like gold, those addresses. With them, you can contact your customers on your own terms, with your own offers. And the customers can take them or leave them.