Turns out many color laser printers lay down a pattern of colored dots that identifies the printer by serial number on every sheet it prints. The idea is to stop counterfeiters, a good idea on the face of it. The problem is that printer manufacturers are not required to tell consumers that their machines do this.
Apparently this practice has been going on for decades.
I remember a few months back reading something about how Adobe Photoshop has some sort of built in system that is used to recognize money that you might be trying to scan into the app, and block it. I’ve never tried it myself to see if this works, but it is not much of a leap to imagine it might also secrety inform someone that you are scanning money…
I guess if you want to print counterfeit money on your color laser printer, don’t fill out the registration card for the printer!