Someone uploaded a copy of the new Harry Potter book to file-sharing networks before it was released. They did this by taking a digital photo of every page.
What they probably didn’t know, and what EFF explains, is the meta-data stored in every image contains, among other things, the serial number of the camera used to take the photos.
Many printers and copiers also imbed their serial number on every page, while CD and DVD burners write a unique serial number to the disc.
Vendors should make these tracking schemes public, and give consumers an easy way to remove them, should they want to. What else is being tracked surreptitiously?