Oh, and about the proper to eat pizza: A civilized person always eats with a fork or knife, unless it is crisp bacon, crudites, or bread. This is practiced in most restaurants in Europe.
However, pizza is a peasant dish, and originally it was a bread dish with some miscellaneous toppings. It being a bread, it is okay to eat with your hands. Because of the hot cheese, it makes sense to fold it over. Chicago style is more of a quiche type or stratta, so using a fork or knife is acceptable. But it's just uncouth to take a whole pizza and eat it uncut.