I've always thought about it as a potential terrorist attack vector. It can be done remotely (from afar) and your target is unlikely to understand what's happening (vs. say a stabbing event). It might be because terrorist events are about spreading the terror more than the damage itself. Still, it is a worrying thought that you could be walking the metro one day and an evil person can decide to end your sight.

Like you said, terrorist attacks aren't subtle, they're designed to kill to incite a political response. This type of non-lethal but injurious approach would be more likely the work of solo psychopaths, the type that try to go undetected.

It's hard to over-state the value and importance of a good A/V crew. They'll keep your speakers from blowing up (or cancelling each other) and, apparently, protect your corneas.