@indigomoth - Actually I know that quite a few performers use beta blockers. People who suffer from nerves in front of an audience, or actors at casting calls or whatever.
It's become almost standard practice for musicians to use them before a concert to make sure that they don't feel too bad and even surgeons will use it if they are worried about a particular operation, so they don't get shaking hands.
But the most interesting use I've heard of so far is for people who are in danger of developing PTSD.
Apparently studies have shown if they are given regular beta blockers for the first few weeks after a severely traumatic event people are much much less likely to develop PTSD. They think it's because of that feedback thing. The brain goes over the event and freaks out again and starts to associate the freak-out with the memory of the event. With the beta blockers, that association is never given a chance to form.