[–] 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!
[–] 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
[–] 5541783? 0 points 2 points 2 points (+2|-0) ago
I think it only applies to inkjet printers (the watermarks are printed using yellow ink on white paper). But don't take that to the bank.
[–] 5542110? [S] 0 points 1 point 1 point (+1|-0) ago
Does inkjet = color and laser = black & white?
[–] 5542326? 0 points 2 points 2 points (+2|-0) ago
No. We have color laser printers at work.
[–] 6304284? ago
There are also black and white inkjet printers.