Many things

[Tony Duell]

> Color laser printers output a serial number indicator of some sort
> by a near-invisible pattern of yellow pixels overlaying the
> printed image.  I imagine it's not 100% reliable but apparently
> it's been in place for some time.

If that's true, it's a darn good reason to use classic printers :-)

If I bought a printer and found it was puting stuff on the paper that was 
not specified by the input data, it would go straight back to the shop as 
being defective. Period. 

-tony