Government Uses Color Laser Printer Technology to Track Documents. As the item notes, the fact that this is being done isn't news, but the stuff about how they do was new to me. Link to PC World story.
Update (10/23): Ed Felton has thoughtful thoughts on this.
At last the government morality police will be able to put names and faces to all those xeroxed asses and put a stop to that pernicious office stunt.