This post brings up some good points.
The first part is that we have to trust people. It is an inherent part of life. For functional reasons some things just plain require help. Ever try moving a gunsafe by yourself? Doesn’t work so well. Also human relationships are part of life and trust is inevitably part of that.
Second trust has degrees. The amount it is reasonable to trust people depends on how close they are to you (including past trust related experiences), the risk involved and your available alternatives.
Along this line beyond direct degree measured in dollars or risk some people might be trustworthy about keeping a secret for one thing but its better they don’t know something else. Maybe Bob can know that you smoke weed but he would freak out about something gun related. Tom on the other hand would probably help you make a home made SMG in his garage but it wouldn’t be smart to let him know about your little horticultural project.
How do we decide the degree to which people are trustworthy? Past experiences such as helping each other,keeping secrets for you, returning items, loans being paid back on time, etc are a good one. If those experiences have not occurred authentically and a it seems like a person could fill a useful role it might be a good idea to test the waters with something small like a loan of an item or telling them something and asking them not to share it before you need their help.
What to do if people become untrustworthy is a question. Ideally by a combination of past experiences and maybe some intentional tests hopefully you can find out about their lack of trustworthiness without it being a major thing. However sometimes things happen. Also people can change or have their circumstances change.
What do we do to limit the risk of problems if someone becomes untrustworthy?
Most of the answer is before a potential issue.
The answer is compartmentalization. This stuff is mostly for intelligence and terrorist types. It works like this.Basically people know what they need to know and not other stuff. The whole picture is broken up into little parts so nobody, or as few people as practical, can possibly blow the whole thing.
Lets say the IRA is going to do a hit. People will only know the part they need to know. The person running the safe house will know some people are coming for awhile (or maybe not even know that). The guy bringing the guns will know to leave them at a certain dead drop between this time and that time. The guy picking up the guns will only know he is picking them up at a certain place around a certain time. The other safe house they go to after will only know their part, etc.
Applying this to survivalist stuff. Just keep your damn mouth shut about stuff unless there is a compelling reason not to. Bob your smoking buddy doesn’t need to know you could equip a combat patrol. He just needs to know you are a good guy and happen to share a hobby. Tom who has helped you on a couple “projects” and with whom you have exchanged just in case foot lockers to store knows about your projects and the foot locker. He doesn’t need to know about your other hobby, or the caches you have elsewhere.
Using compartmentalization limits the risk if any person, for whatever reason, becomes unreliable.
So those are my thoughts on that.