I know many Americans have a strange regard, if not dislike for their postal service and it's inefficiencies - so they may think this odd:
..the Mail Isolation Control and Tracking program, in which Postal Service computers photograph the exterior of every piece of paper mail that is processed in the United States — about 160 billion pieces last year. It is not known how long the government saves the images.
Link:http://www.nytimes.com/2013/07/04/us...pagewanted=all

That must be some computer database, even if only retaining the photos for thirty days.