DRM Cruel

This may be something like allowing them to play right up to the very end of the game but just before, show a message stating the game is an illegal copy and leaving a reset as the only option to continue. Or the illegal copies of the game will allow the player to advance only to a point but subtly prevent further advancement in such a way as to make the player think they can still advance if they play well enough.

Infocom's Spellbreaker might be the most extreme example of this and can easily inflict it's cruelty on ligitimate customers as well as illegal copiers. No matter what answers you give for the copy production questions, even typos, the game will report success. But if an answer was wrong, the very last puzzle of the game, reached many hours to months later, is not solvable with no indication of unsolvability.