Lots of things can drag down the value of a home to zero. Lack of maintenance or a natural disaster are two big ones, but also the neighborhood could turn to crap or an infrastructure crisis that isn't resolved.

Add to that property taxes continue to accumulate on buildings. There are quite a few ways to drive a house to worthless. I used to live in a region where houses were <$10k because they were condemned shells in crime-ridden areas.