Well
@andrewOz , I get your point.
A few Questions:
A. Would you let someone enter (or even "adopt") that does not seem rational?
B. Why would any irrational acting person won´t shoot you on sight and then plunder your preps?
C. How many time will elapse until rational "tramps" will shoot you on sight, just because your existance means that there is something to find?
A. Sometimes there are people who, through no choice of your own, become part of your "group". Examples: step-children, in-laws.
(Case-in-point: I had step-children, whom it was agreed would start being responsible after they emigrated to here. That never happened, and they remained sloths, treating me as a slave for years. If SHTF had happened, and I had a BOL, I probably would have just executed them if they continued with that behaviour. As it turned out, their behaviour and their mother's refusal to employ any discipline ultimately resulted in the breakup of the marriage. Problem solved!)
B. There are probably many reasons. A couple reasons: they might want (a) slave(s) or sexual object(s).
C. Not much time at all; days, I reckon. Which is why one's BOL should not be near roads on which "refugees" are likely to travel, and should be as remote and difficult to get to as possible. And, ideally you should be aware when people are approaching your property, while they are still a distance away (or have a large enough community of like-minded people that an intruder can be repulsed*).
A big danger in Australia, is the heavy limitations on HONEST people to own adequate weapons and stockpile ammunition. Which means, (govt and non-govt) criminal gangs will be the ones with the most firepower, capable of pillaging the countryside almost entirely unopposed.
*I encountered such a community up a certain road in northern New South Wales, but the price the vendor was asking for the land he was selling was too high.