The building has a guard on duty at the building entrance 24x7. Everyone has to use their card to enter the building through a turnstile, and everyone has to use their card to enter the datacenter. If you forget your card, they issue a temporary one after checking your ID and verifying you against an on-file picture. Your regular card is deactivated until you return the temporary card. Guests are issued a temporary card, good only for that day, and must be signed in by the person they visiting. You are supposed to display your badge at all times, but no one does.