There's an emergent interaction between PWM headlights and rear view mirror cameras(RVMC)[1]. The PWM headlight frequency and RVMCs frame rates are slightly different and phase in and out of each other resulting in a strobing effect. If RVMCs become more popular, eventually an accident will result in the way these two technologies interact. I found it an amusing interaction, but it also has serious safety implications that should be addressed.

1. I'm not sure if there's a better name, but the system where the rear view mirror is a display linked to a camera at the rear of the vehicle in higher end cars.