In addition the systems are not infallible. Las Angeles County had to return over 500,000 in fines because of problems and malfunctions. Other areas have been caught actually shortening the yellow light timing to increase the number of people running the light. These cameras are big business and money talks.
In one city the judge will automatically dismiss the ticket if you plead not guilty because of the problems. However they fail to tell this to the numerous others who just send in their money.
The cops and camera companies tell you the spray does not work. Other reports are mixed. For the money it is worth it if you live in an area with these cameras. After you spray the plate place a couple of washers under the bottom screws to tilt it slightly upwards. Along with the spray this helps to distort the numbers.
Here is a link where you can order and find more information. Currently offering one can free when you buy two.
Phantom Plate Specials