It's been a while since I read them, but I remember a few Rumpole of the Bailey cases where Rumpole used his encyclopedic knowledge of typewriters and how different typists emphasise different letters to great effect. It always seemed a little sad to me that in this age of laser printers and thousands of fonts that all that would be lost.
Well, it seems that the manufacturers of laser printers thought so too, or perhaps had other motives, and made it so that each printed page has a microscopic configuration of dots on it that tells you the id number of the printer and the time and date of when the printing was done.
Boing boing knee-jerkedly call these snitch codes and they believe "that this is done to get your equipment to incriminate you without your knowledge". Well, now it can incriminate you with your knowledge.