I don't have the time to do this, but maybe someone out there does? Feel free to take this idea.
A web site with user accounts that has a location field (area code?). The ability to, via text message, email, or a function on the site, to submit a license plate of a bad driver. The license plates are grouped according locations like Los Angeles, or states. The state might be set in the user's account, a default state for submissions maybe?
There would be a few false positives, naturally, but the real offenders would show up. This might even be a more useful site for bike riders and pedestrians.
I can also imagine there could be discussion beneath each license plate entry.