Underground homes make excellent sense on many levels, from cost of materials to insulation to saving land space for greenery, to safety from hurricanes and tornados. The list goes on. Even the lowly rodent is smart enough to make its abode underground.
And man? Much to intelligent to do something like that. Man would rather fight with nature. Guess who wins?
I think in some places this would be pretty dangerous... floods, earthquakes, etc?
I'd go for an underground house here we don't get many earthquakes and they are pretty small at that (Nor-CA) but it would need to be over engineered to make me happy.