It's a pity concert halls etc. don't distinguish between flash photography and non-flash.

I never use flash in such a venue, as I realise it's annoying for other members of the audience, and off-putting for the performers. But I don't see any harm in taking pics without flash (as long as you don't obstruct anyone else's view of the stage). The results are often better too, subject to being able to keep the camera steady. It depends where I'm seated - if I am at the front of a balcony I can rest the camera on the wall/rail. If not, then the results can be blurred, but I've taken some pretty good pictures in the past on a small pocket sized digital camera.

It seems the thoughtless 'flashers' (ooerr missus!) have ruined it for all photographers :-(