The main reason they tell you not to eat carbs at night is because most "regular" people eating the traditional american crap diet have reached their caloric intake by this time of day.
This is probably not the case for most bodybuilders. But make no mistake, any type of calorie, carb,fat, protein, that is consumed over your caloric maintanence(sp) will be converted into fatty acid chains and stored as potential energy (bodyfat).
For the health minded individual, also the type of calorie eaten is very important. 3500 calories from candy, ice cream, and pastries have a low nutrient density per calorie. Which means when you eat those types of calories, your body is not getting the nutrition that would come from a clean 3500 cals.
Think about it. After you have just finished eating some crap food, minutes later you are hungry even though you just ate. Some of this may have to do with blood sugar levels that rise very quickly then dropping quickly. But i have a theory that part of that feeling is the body is still hungry. Not hungry for voume, but still hungry for nutrition.
High nutrient density per calorie is the goal of the healthy eater.
This way every calorie counts for you -- instead of against you
Sorry for being so long winded.