Any time I have more than one or two friends over, they might park a car in front of my neighbor’s house. She will go put print outs on the windshield of their cars saying, “You are parking here illegally. If you continue to park here … It seems to me that would be very strange – my neighbors talk about all kinds of things, and pretty much only nice things, but it would be very weird to live in a neighborhood, watch someone come and go and never say anything about them! … …

More here:
“The Water Cooler”: Have you ever had a dispute with your neighbors?