The problem with this is that the video app (or a contextkit provider) doesn't remove the title when playback is stopped. All Billboard does is read the Media.NowPlaying contextkit property. I'll see what I can do, but no promises, especially since querying the active applications and monitoring what is closed and so on could lead to decreased battery life, so I might end up not fixing it for battery consumption reasons (just relying on contextkit makes sure that the display is only updated when something changes, and also that Billboard doesn't have to do any additional monitoring, which is light on the battery).

If you have to watch videos with titles that you are embarrassed about, just take a few seconds afterwards to open the music player and start/stop a song - this will clear the display. Or just remove the currently-playing media fields from your Billboard settings