I think that keeping a secret is often a pretty difficult task, depending on the content of the secret and the bar of nondisclosure you're trying to maintain. In particular, I now think more than I used to that:
- If I ask someone to keep something a secret, I don't have a very strong guarantee that the secret won't spread further, even if I think I've made it clear to them that this matters.
- If someone asks me to keep a secret, I should think about it before learning the content if possible, ask them some meta-level questions about the topic, and potentially decline to hear the information.
- There are some kinds of secrets that I am just bad at keeping, and cannot credibly promise to hold. This is probably also true of many people who don't yet know this of themselves.
- In particular, secrets that involve me taking a piece of information I'd normally model as public like "I'm going to be out of town next week" and rendering it classified are very tough for me to consistently track if I'm in an environment where my knowledge would ordinarily be relevant.
- Telling someone a secret without their consent and only then saying you need them to keep it quiet is a bad social move.
- Incurring secrets with very high bars for leaking any bits about the topic at hand is actually super costly if taken seriously.
Why do I think this? Being a scrupulous secret-keeper means tracking, for every action you ever take, whether it leaks information about secret S for all secrets S you have ever committed to not revealing. This is an enormous amount of cognitive labor in general! Your only hope of being a functioning human is to restrict the set of secrets you ever take on, to restrict the scope of those secrets (in time or context or recipient), or to lower your bar for how good you will be at secret-keeping. In practice I think most people do the latter and don't really notice that they've done so.
(There are some other strategies you could adopt, like making all the rest of your actions sufficiently weird and confusing at all times that it's much harder for anyone to work out what you think about the world, but these are also very costly.)