I personally believe that the power will always ulitimately rest with the diner. Restaurants, after all are a buissiness and they require returning customers inorder to stay in business and continue serving the food they love. In the restaurants I've been lucky enough to work in, the chef will honor just about any request that isn't physically impossible. You'd like a Pritikin(no fat, no salt) Caeser Salad? No problem. A four course mushroom tasting menu? We can do that. One out of every three tables seems to have a special request(SOS, no cheese, gluten intolerant, alergic to nuts, alergic to onions, no garlic, no alcohol, etc.). Some of the more unusual requests are entertained by the front of the house(in hopes of scoring a larger tip) and are then foisted on the back of the house, but it generally seems beneficial to everyone to comply with such requests. The axiom that the customer is always right seems to hold true for the most of the restaurant industry. There does seem to be exception, and that is the stratosphere of the culinary pantheon, the kind of places with just tasting menus, as those are the dishes the chef wants you to have in that exact order. Chefs at this level aren't often willing to compromise what they see as their 'gastronomical vision', and will probably not heed your request to have a shrimp cocktail for your second course, but I would be suprised if chefs at this level didn't honor simple food alergies or requests for the sauce on the side. The power will always rest with the dinners as long as there is a choice of where to eat. And regardless of how mind blowingly amazing the chef thinks his food is, if other people don't eat it, enjoy it, and return, then he is going to be out of business very soon.