How do breakaway helmet accessory mounts work? I've seen it said that when mounting things such as a light or camera on your helmet you want a breakaway mount so that in the event of a crash the helmet slides along the ground rather than snagging on it.  What is it about these mounts that lets them break away?
My Light and Motion helmet light has two built-in weaknesses that seem designed to fail on impact, tearing the light away from my helmet and not allowing any impact torque to transmit through to my neck:


The light and battery plastic mounts (the plastic-to-plastic connections) are intentionally weak and will pull away with very little force
The velcro that connects the mounts to the helmets isn't very strong and would tear if there was greater lateral force on them


I haven't tested the breakaways in an accident (and don't hope to) but I can say that the light and battery have released when I've hit them on low ceilings in my garage, to my chagrin.