By informing a consumer of the number of calories in a food item restaurants are simply providing one with information. What you do with that information is ultimately up to you. People should be able to make the right choices for their health but millions don't. It is nobodies fault but your own if you are obese, you made the choice all by yourself.
Calorie counting on menus does effect obesity. It shows the overweight person that the restaurant is encouraging weight loss and therefore the obese person would want to think twice about having a double dose of deserts for an example. Calorie counting is one way of combating obesity in public restaurants,
Fat people have gotten fat either because they are and don't give a crap or haven't been watching their diet and physical activity. The simple counts don't help because nobody looks at them. Sure there are some dieters that will look at them. These dieters just lose weight and feel good about themselves but then are off the diet and are right where the started and gain weight again.
Calorie counts do not respond to the obesity crises. Just because you label something does not mean everybody is going to read it or use it as a diet. There is too much emphasis placed on the obesity of society and we all want to look like the person in the magazine. Those are mostly photo shop images or stereotypes.