So, Swiss Post offers a "print and send a postcard with a photo of my choosing" service and gives everyone one such postcard free[1] per day. The canton of Zürich has an opt-out publicly readable mapping from license plate numbers to owners' names and addresses.

So, does anyone have some nice artwork for "please check your headlights", "thank you for being considerate", "please remember to use your turn signal", "please don't use a cell phone while driving", ...? :)

[1] well, ad-supported: they put an ad on the back next to the text