[–] 5541135? 0 points 4 points 4 points (+4|-0) ago
Good question. I have heard this before, but I don't know if it is true.
However, I do know that most of the time a printed page can be matched up to the printer it came from because every printer makes minor copying errors that can be matched like a fingerprint.
But you would have to know what printer to look at to make the match.
[–] 5541156? 0 points 3 points 3 points (+3|-0) ago
http://www.instructables.com/id/Yellow-Dots-of-Mystery-Is-Your-Printer-Spying-on-/
I guess it's not always micro
[–] 5541475? 0 points 2 points 2 points (+2|-0) ago (edited ago)
Not all, but many are:
EEVblog #825 - Your Printer Is Spying On You!