[BenLurkin]

Interesting, thanks!

You know, in this digital era the studios could code each 'print' and then track the persons who have access to that particular print. If for some reason they suspect someone, they might even slip him or her a uniquely coded print and see if it turns up on the market.

[kingu]

They do that to a point with 'screener' copies of movies. The biggest difficulty is that the source video is re-encoded and re-sized - making most creative efforts to track the video pretty useless. The most effective scheme I ever saw was done by Disney - they simply put a 'Security code -- 2919293' (a different number for each copy) in the credits at the end of the film.

A lot of major newspapers got egg on their faces as copies were located in China, Iran, Saudi Arabia and France. Simple sound queues or spacing of initial credits differently could easily be used to identify which copy is which, but as I said, they like to get really sneaky and it nearly always backfires. (Damn those pirates, finding out our security system! -- what the pirates actually did was re-crop the film for television, slicing off the ID codes.)