Cecil wrote about this back in 1991:
http://www.straightdope.com/columns/read/1058/do-maps-have-copyright-traps-to-permit-detection-of-unauthorized-copies
There must have been long-ago discussion, that got picked up and we’ve now got a book and upcoming movie. Thread and discussion is in Cafe Society, since it’s not really about Cecil’s column. See and comment here: In NYT story author got inspiration for story from the Straight Dope & book is now to be a movie! - Cafe Society - Straight Dope Message Board