Apparently public service workers in the Netherlands get beat up all the time... and everyone just watches and does nothing to stop it.  How do you change this behavior?  Create an alternate reality where it happens right in front of you, and then tell people how they should react.

Normally I'm not a big supporter of billboards, but this one works because it is a perfect fit among media, message and audience.  Hat tip to PSFK on this one.