http://www.techtree.com/techtree/jsp/article.jsp?article_id=68717&cat_id=582
"The Electronic Frontier Foundation [] has analyzed codes embedded in printouts in color laser printers. The code cracked by the EFF was an invisible bar code that contained the serial number of the printer for tracking users as well as the date and time a page was printed.
In Xerox printers the code appears in a pattern of yellow dots visible only with a magnifying glass and a blue light. The codes are supposed to be for government agencies looking out for counterfeit currency printers.
The EFF said it has identified similar coding on pages printed from virtually every major printer manufacturer"
List of Printers Which Do or Don't Print Tracking Dots:
http://www.eff.org/Privacy/printers/list.php
So do photocopier's "carry on" the dots?
My guess is "yes"... assuming the scanner can see them.
Now, what about a completely yellow page? :)
This is vaguely related, and is also a fun game to play with any bills you can get your hands on:
Picture of the laser dots here:
http://www.humblefool.net/news/res/190.html
Heh, both of mine are under "yes."
...Not like I print anything besides homework, anyway.