I took this off the Montgomery County, Maryland site:
Q: Isn't it an invasion of privacy for a speed camera to photograph my vehicle without my permission?
A: No. Individuals who are breaking the law are not entitled to privacy according to established court doctrine. Speed cameras only take photographs of vehicles whose drivers choose to violate traffic laws by speeding. When motorists apply for a driver's license, they are agreeing to abide by the rules of the road. The purpose of speed cameras is not to invade the privacy of citizens, but rather to detect motorists who violate the law and endanger the lives of other motorists, bicyclists and pedestrians.
I know, it is contrary to the public opinion, but, we should not be so willing to give up any of our rights. What's next?