Two of us went to Centurion with a Groupon for brunch. We arrived at 10:45 am and were told that we could not use the Groupon and they would only honor it until 10:30 am. We asked if we could apply it to lunch and we got a firm no. They said it was Groupon's fault because it was supposed to state breakfast and they printed brunch. That isn't our fault. We went somewhere else for a late breakfast and happily gave them our money. It is tacky and defeating to turn customers away. We will never go back and we will be sure to tell everyone we know about this.
By putting things on Groupon you stand a good chance of aquiring new and loyal customers. Turning people away is not a great way to build a customer base.