The pages coming out of your color printer may contain hidden
information that could be used to track you down if you ever cross the
U.S. government. Last year, an article in PC World magazine pointed out that printouts from many color laser printers contained yellow dots scattered across
the page, viewable only with a special kind of flashlight. The article
quoted a senior researcher at Xerox Corp. as saying the dots contain
information useful to law-enforcement authorities, a secret digital
"license tag" for tracking down criminals.
Similar embedded control and tracking coding seems a likely and probably would be useful for even limited nano-factories. It would require hacking to circumvent and time to detect. It could slow up and deter some forms of abuse. It would be a constant battle to increase the barriers to abuse to those with sophisticated skills.