[PCI DSS 3.0] 9.7.1 Properly maintain inventory logs of all media and conduct media inventories at least annually.

9.7.1 Properly maintain inventory logs of all media and conduct media inventories at least annually.

9.7.1 Review media inventory logs to verify that logs are maintained and media inventories are performed at least annually.

Without careful inventory methods and storage controls, stolen or missing media could go unnoticed for an indefinite amount of time.
If media is not inventoried, stolen or lost media may not be noticed for a long time or at all.