For a lot of the examples being given in this thread, like billboards and movies, I'd actually welcome an orange dot notifying me that audio is being recorded - since that's not an expectation I'd otherwise have. Though this probably isn't what Apple are trying to do, and would need to be enforced to prevent circumvention.

The initial example of live shows (specifically the subset of which where the same device is being used for some kind of audio input and visual output) is so far the most convincing example because the orange dot is redundant there.