There is a distinct possibility that restaurant owners approved the deal with Groupon but staff is left to suffer the consequences, possibly with little warning from management or the owners.
The restaurant business is not exactly raking in the big bucks right now, with the continuing (and deepening) recession, and the owners may have signed on in desperation to claw out whatever money they can.
I'm not sure how it matters what part of the company went wrong. As a customer, you only care about the end product. You don't care whether an owner or a waiter failed to do their job. The responsibility for the failure always lies on the business.
The restaurant business is not exactly raking in the big bucks right now, with the continuing (and deepening) recession, and the owners may have signed on in desperation to claw out whatever money they can.