I work for a restaurant that uses Opentable for reservations. Someone made a reservation online with the note "it's my husband's birthday, so please send out a dessert with a candle" (word for word quoted). We brought out a dessert with a candle, and she paid the bill. Now she's calling me saying she didn't want to make a scene at dinner, but she expected the birthday dessert to be complimentary and wants the money refunded. I quoted back her request, and told that that constitutes an placing an order, which one should expect to pay for. All of our desserts are the same cost, so it is not as if we picked the priciest dessert on the menu to gouge them, we were just trying to accommodate her simple request.
If you were the customer, would you expect to pay? I know my feelings are obviously screwed working in the industry, so I'd be interested to hear what general expectations are.