I have a bone to pick with Canon... There are two settings on a Canon DSLR regarding the memory card. You can either shoot to your hearts content without a card (and obviously record no imagery) or you can set the camera not to shoot (rather to give you a "no card" warning in the viewfinder). IMO, the default setting should be the latter but, Canon has its default at the former.
No problem if you read the instructions but many photographers go by the old saying "If all else fails, read the instructions"