When the player has solved my puzzle, I play a video using Handheld.PlayFullScreenMovie, which pauses Unity during playback and offers no control over the volume of the video. My game itself has separate volume controls for sound effects and music. If my player has turned the volume down or off in the game, the video's music will be an abrupt blast of sound, waking the baby, upsetting the librarian, making the cat jump 7 feet.
I don't want to put up a dialog, "Play video? Its volume is out of my control. OK/Cancel" because it would ruin the moment.
I could play an alternate version of the video without sound, but it will add a few more MB to my project, and I actually want to reduce the size.
I could just not play the video if the volume is turned down, but it makes for a more abrupt and less satisfying ending.
I'm thinking of doing a compromise: have a small, heavily compressed version of the video with no sound, and play that when the volume is turned down.