Automated speed trap systems increase revenue because they avoid the costly overhead of paying a real policeman to write tickets. And since revenue generation is the whole point of speeding enforcement, such automated systems are an easy sell with police forces and politicians.
They are are so eager to implement these systems, they must not test them very thoroughly, as is this story from Australia demonstrates. One would think that a flaw in an automated speed trap system, would be grounds for automatic refunds for all the tickets issued by the system, but apparently it is not. After all, that's a lot of revenue to give up.
I wonder if my brother was caught by this system. He has been known to drive briskly on the odd occasion. ^__^