pairs - x-codes and trending graphic devices

i've been watching a lot of the post-katrina television series 'Treme' by the makers of the Wire recently, and was struck by the similarities between the x-codes used by search and rescue teams to mark abandoned and damaged houses, and the crossed lines and text logo's favoured by graphic designers over the last few years. 

I am not sure if there is a connection between the two, but i hope there is, and someone tracks down the first instances of emergence.

also, i haven't used blogger for a while. the new interface is pretty average...