I was passed this evening by a silver Audi sedan which had a very interesting license plate. CA plates are normally blue lettering on a reflective white background; this guy had taken what appeared to be small white dots and stuck them onto the blue lettering, almost completely obscuring the blue paint. Unless you are right on top of it, the letters on the plate blend completely into the white background. If these dots were reflective, and I suspect that they were, this would render the plate completely illegible to red light cameras, speed cameras, and anything else that uses a flash.
It seems like a cool idea, but if I were to put those things on my license plates I would get pulled over within 5 nanoseconds. I guess if you drive a boring silver Audi sedan cops don't notice you.