No, I don't mean a sign where the top bolt fell out and it swung down. And I don't mean a sign that looks similar both ways such that it could understandably be accidentally flipped.
I mean this:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fimg713.imageshack.us%2Fimg713%2F8970%2Fdscn8127r.jpg&hash=be8a7d085ad5c28108df329f03614e7d6857d891)
Not just one sign, but an assembly of two signs, clearly quite deliberately hung upside down!
I suspect this was done by a couple of juvenile pranksters.
Note that street view (http://maps.google.com/?ie=UTF8&hq=&hnear=New+York&ll=40.845307,-73.840828&spn=0.003539,0.00795&z=17&layer=c&cbll=40.845226,-73.840754&panoid=-g8p4BAwDmnBEuu-TBEd0A&cbp=12,0.57,,1,-2.9) depicts the sign in question right side up.
This reminds me of a time when someone hacked one of those electronic warning boards to say "WICKED CURVE AHEAD" instead of "Construction Ahead" or w/e.