John, when I was in Germany back in the late 60's photo radar was common place. The supposed way to obscure your license plate was to paint it with 6 or 7 coats of clear spray paint. In your experience do you think that would have worked?

I doubt it. My understanding is that the purpose of the laser diffuser is to send parts of the laser beam off in different directions so the sending unit does not get a good reflection (like the Stealth fighter's angled surfaces). Police usually aim the laser at the front license plate because it is a good reflective surface; but depending on the shape of the front of your car, the laser beam might just as easily bounce of some other part of the front.

Photo technology is different. The license plate covers I bought are also supposed to make the plate appear blurred to a camera. I think it does the latter quite well. If you look at the plate on a side angle, the numbers easily become unreadable. I have accidently gone through the permit lane on Chicago freeway (88 & 294) and I assume camera took picture, but no ticket. Ergo, it worked(?)

Also see:
http://www.fortunecity.com/silverstone/berger/364/pjs.html

In my lovely state, if you cover your plate with anything, it is a $50 or $100 fine.