There's another angle here that isn't even covered by CASA regulations. I don't know about others thoughts - but a drone weighing say a kilogram or two, suffering a power failure at the height of a 50 story building, and falling into a crowded suburban street, is almost certain to cause injury to persons.
The CASA regulations only cover the possibility of personal injury created by, or after, collision with an aircraft in the air.
AFAIC, those regulations are inadequate, and I believe it should be illegal to operate a drone where the risk of injury to innocent persons on the ground is high, if it falls from the sky due to mechanical or technical failure.
Drone Operators to be handed guidelines on operation