I love the idea behind this Google Maps mashup. As Zapatag.com say themselves the map lets you,
"Report bad drivers, track license plates, zap a tag and upgrade your commute. Compliment a carpooler. Lash a litterer. Tattle on a tailgater. Snap at a speeder. Bring accountability back to our streets the Web 2.0 way. Don't get mad on the road. Get even online."
To use the site you simply enter the licence plate number of the car that has annoyed you and enter a location. Zapatag.com then places your message on a Google Map. It is possible to browse through the messages submitted by other users by state, by the latest zaps, by the most commented on or by most favourited.
Just don't zap whilst driving or you just might find your own car listed on the map!