There are a lot of factors that can come from screen cracking. I've seen Droids crack and some not, some DI's crack, some not.
It depends on how it dropped, how high, where on the phone it makes it first contact with the ground, the surface of the ground itself, if you decide to throw it in a rage, what planet you are on etc....
Mine fell last night from about 4 feet onto a thin piece of carpet like they have in offices. Only nicked one tiny bit on one corner and it cracked on the opposite corner. I also have insurance.
Were you able to get an insurance replacement in the store? or did you get it shipped?