I had stuff like that happen to me when I lived in DC so much I started carrying a small notebook and a golf pencil for license numbers. I lived in a condo building that happened to house two officers, one of which would take those plates, and when in the right mood, put the fear of God into the people. Without an inside source, I'd still say report it. I believe they keep track of those reports and if they start getting the same guy over and over they'd probably take action. Might not help you, but eventually it should thin out the herd a little for all of us.