exif tag id is 16 bits value, only a few that have been populated. there are plenty of room for user/manufacturer/governmental specific data that can be held classified from the mere mortal's knowledge.
a) EXIF data does not impact the image, it is not lossy steganography.
so does not the pattern in the print out
b) EXIF data can be removed and viewed with any photo imager software. Heck, even Windows Explorer.
so can the pattern, its now possible through knowledge. thanks to this thread and the accompanying video.
c) EXIF data is not and was not government mandated
probably one out of the 2^16 Exif's Tag ID can be... through governmental and manufaturers / Exif committes closed table meeting.
d) EXIF data is part of the JPG file format specification, which many professional camera users avoid because they use RAW mode which does not have EXIF data in the image.
JPG was born 1991, Exif was born 1998, obviously the original JPG was not supporting Exif. RAW is manufacturer's specific format, what metadata contained inside is anyone's guesses.. and err.. most professional users (with senses) that are not obliged to shoot RAW will shoot in JPG..
e) EXIF data does not have the serial number (although that's possible I believe, but I've never seen it, as it adds no value to the user). EXIF is not designed to track users. Some modern ones have GPS, but most products let you disable that.
in current Exif specification.... 0xa431 is tag for serial number, 0xa214 is subject location, 0x8825 is GPS info...
http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/EXIF.html...your own serial number may not be usefull to you until you lost the device, hoping one day a picture popped out in the net with exif "0xa431:your serial number" in it...
And my question was if the camera added yellow tacking dots or something else to the actual image.
very unlikely the "real finished product" will be smeared with this spy info, just as its very unlikely (through common sense) that the yellow pattern will be printed on the printed out image or dark area...
just think of the printed area on the paper (area that are smeared with inks from image/document input) as the JPG compressed data storing imagery, and white area on the paper (with the yellow pattern) as the Exif metadata area in the JPG file.
edit: an interesting experiment should be fun. print a full black (or full color) page, borderless if supported and see where the pattern will be...