I don't think crack screen will apply to the warranty term and condition.

Apple sell their OneCare separately anyway. You can buy that package whenever you like. And even on an old Iphone 2G as long you still haven't opened it. But yeah I just wish they have a JailBreak spy in the OS. And cannot downgrade OS like Nokia.

For example: N900 cannot downgrade to lower version once you've updated. You can downgrade it but your phone reception will be dead. I think this is a best way in term of protection ever.