lymph
Enlightened
Apparently, many major color printer manufacturers are encoding your print-outs with nearly invisible blue dots. These dots encode the printer's serial number and the time/date of the print-out! You can see the dots with the aid of a blue LED. Check out this article about the people who cracked the code:
http://www.tgdaily.com/2005/10/19/eff-decodes-printertrackingdots/
http://www.tgdaily.com/2005/10/19/eff-decodes-printertrackingdots/