No means no.
Use common sense. There are definitely situations where you are definitely not allowed to use flash.
Remember that people get distracted with sudden bursts of light! Be courteous. In this shoot, I would have messed up the dancers when they were doing their routines. The flash would have been extremely distracting.
Again, use common sense. Swim meets? No flash. Most sports? No flash. Again, flash is distracting. Even if you get permission from the venue or the organizer to use flash, think twice before you start using your flash.