The Big D

[Trey Reese]

Guys, I've noticed several houses in my city that have several LARGE red "D"s spray painted on them.  These are run down houses (typically in more run down neighborhoods).  Most of them have the windows boarded up.

Does anyone know what this means?  Maybe the city has tagged as 'derelict'? 

I've seen it across at least 5 different neighborhoods.  Always "D"s, always red.  Always several of the same size on the front of the house (doesn't look like kids messing around).

Thoughts???