It's not to disguise the wearer, it's to feed junk data into any license plate reader that happens to look at you. I don't think it's really useful, but the idea is that if the systems get filled up with enough junk data, it won't be worth it to maintain the systems if they have to sort through a bunch of nonsense every time they want to search for something.

Maybe I'm missing something, but wouldn't they just do an automatic lookup against a nationwide plate db and discard ones that don't match?

How do you distinguish between ones that don't match because they're invalid or ones that don't match because the algorithm didn't properly process the image?

Also, what stops you from using real plate numbers? It's not like they're hard to collect -- unless somebody passes a law against that.

It seems like you could cause some real confusion if you lived near one of these cameras by putting a screen in your window that cycled through random plates. Especially if you run your own ALPR on the street and only use plates that have passed by before.

I wonder what the rules are about displaying license plates on your car. No doubt you're required to display the one issued to the vehicle, but what happens if you also cover the car in pictures of different ones?