Speed bumps slow down speeding motorists - camera's don't.
Once people get used to the presence of these average speed camera systems, it will either divert traffic to a road zoned for faster speeds or get them to slow down.
I don't really care about the privacy aspect, because if the cops want to see me picking my nose while I'm speeding, they're more than welcome to it. No, I don't like the fact that they have another way of giving me fines.