One of the best and most clever forms of copy protection is the reward principle: Those who buy the product get goodies that accompany the product, which are unattainable for those who just copy the product.

One company that excelled in this kind of "protection" was Infocom. Their text-based adventures always had loads of gimmicks that were just plain cool, and desired by anyone who also liked the games. Patches, forms, comics, maps, etc. Every product had it's own gimmicks, never repetitive, always fresh. This meant that many people, who could (and would) have just copied the discs from friends, went out and bought the games instead, just for he gimmicks. In fact, this is one of the main reasons of the high collectability of Infocom adventures, and the high prices these old games, written for machines no one really uses anymore, are still that high.

So what is the lesson to be learned? Give the buyers of your product something more, something that can't be copied, to be desired. Give the CD a special case, include trading cards, pins, special extra DVD's or posters with your DVD-releases (very popular now in Japan). Loads of special features also help. That way, you do not need to anger your customers by including copy protection measures that hurt legal customers as well (such as Macrovision, incompatible CD's, etc).

Make your customers feel good about the purchase, give them something that makes them happy about spending the money. Don't treat them like your enemies...