Roonil I think that it would generally be strangers who would be feared and dangerous.
I read somewhere (that elusive 'somewhere'!), that groups of people who are neighbours and know each other relatively well actually do come together for support, trade, sharing of skills etc in time of absolute crisis. A close knit group would be able to defend their properties from outside looters, thieves and general trouble makers etc. and generally do much better than individuals would in getting through a national crisis.
One tip that stayed with me (I sometimes read the 'when the shit hits the fan' forum on money saving expert) is to stock up on non perishable items, like loo roll, matches, toothpaste, tampons, alcohol etc etc that you could use to trade with someone else who has something you need. Clearly it would seem a bit daft to go and fill your spare bedroom with these things, but if some sort of trouble looks like it's brewing, it would be possible to stock up a bit in advance.
I think the crucial thing would be not having to leave the home and face outside danger, or if you do have to travel do it immediately before it becomes more dangerous.
I'm scaring myself now 
I honestly don't spend too much time thinking through Armageddon scenarios....(and I definitely don't tell DH, he doesn't take it seriously, at all)