Rocks thrown, sensors spray-painted over, side panels (and sensors) graffitied, interiors damaged, forced into stopping and their chassis stripped (or their occupants held up).

And while the police may be quickly notified, they will not be so quick to respond. Ask someone in a big city about the police's response time to their car being vandalized or stolen... Not to mention, all those fancy cameras? Ask a small business owner with CCTV how useful it is to catch robbers.