actually nbk2000, that's my old nickname. When I did mention Japanese castles and the way they are laid out internally, it is because in traditional houses much of the same is imitated. What I essentially mentioned are passive defenses that could be incorporated into any blueprint for a home. The best defenses are unseen. I think these are better than having active defenses such as explosives, which require a high degree of maintenance and awareness, which are a potential hazard to welcome guests and residents alike.
From what I understand, in Brazil where home invasions are common, architects are now designing buildings with added defensive value (rose bushes on the perimiter, for instance) rather than strictly following aesthetic designs. The LA Times had a profile on this 2 years ago or so.
Basically the best "fortifications" I think are those which:
(1) Either deter through overt defenses or remain well hidden
(2) Channel BGs who chose to enter, impede their progress and actions, and set off warnings to the householder
(3) Keep the householders (loved ones' bedrooms far away, etc) well out of reach but enable escape as well
(4) Spatially laid out so that a few can engage many if open confrontation is the only recourse.
Wow ... this thread is getting long.