You can find such ideia working in Brazil and other countries in South America. It has worked very well until people began to remember where the fixed radars were placed. People run, brake close to radar and then speed again. Then government had the other idea to place mobile radars.For more info try http://www.dersa.sp.gov.br/rodovias/radar.asp

Picture two cars on a four lane highway in a 40 mph zone, one traveling at 40 mph, one at 60 mph. They both get to the point the camera snaps the picture at the same time. Your camera goes off. Who gets the ticket?

Cameras have no judgement. A police officer can observe which vehicle is overtaking the other and issue the ticket to the correct party. The camera would likely ticket both. And if I was the guy doing 40 there would be no way to prove my innocence.

Photo radar is what it is called. Ontario Canada tried that, but quickly abandoned that (not sure why exactly). AFAIK there was a cottage indusry making/selling license plate covers that the camera flash would obscure.

This is already being implemented in Arizona (US) cities which use it at intersections, on main roads, and on highways. It is effective and useful here, and apparently accurate.

I received a ticket for running a red light with a camera. It came in the mail with my picture in the intersection. I was very angry because the picture clearly showed a city bus right in front of me that blocked my view of the light and also came to an abrupt halt that stranded my in the intersection. Like the previous poster said, "cameras have no judgement". I would not have been ticketed by a human in that case.

Someone is a little out of date here. This has been going on for years in most European countries.
Look up "speed camera map" in Google.
It is very effective, and either very popular or very unpopular depending on your bias.