A common argument against the existence of conspiracy theories is that large groups of people are unable to keep secrets, so the existence of the conspiracy will inevitably leak to the public. How can thousands of people be involved in a moon landing hoax, UFOs, or 911, and not have at least one of them spill the beans. I suppose it’s supposed to sound clever or be plausible given how humans love to gossip. However, it ignores the evidence that it is indeed possible for large organizations that employ hundreds or even thousands of people to keep secrets for a very long time if the incentives are strong enough.
Iron clad NDAs do work. This is why the Snowden and WikiLeaks documents were such a big deal, owing to the extreme rarity of such leaks, and even then, only a small amount was actually divulged. The most important stuff, that is most applicable to individuals, is still under wraps, and it’s safe to say it will stay that way. There are tons of Google searches that ask “how do I know if I am under investigation” or “what surveillance techniques do agents use,” and none of the answers are satisfactory or even correct, because that information is under wraps even after many decades and hundreds or even thousands of agents who do know. Any agent that divulges such information, not only would they void their generous pension, but it would also open the leaker to a criminal investigation (see what happened to Robert Hansen to see why this is not a good idea). That is a pretty damn good reason to stay quiet.
Another example is search engine algorithms, as well as algorithms for major social networks such as Facebook. Even after almost 2 decades and thousands of Google and Facebook employees who have come and gone, all search engine and social media consultants have to go on are hunches (much of SEO is just guesswork, trial and error). There are people who do know how Facebook or Google’s algorithms work, and may even code or design them, but NDAs, again. Google and Facebook have among the most generous of salaries in the world and the most dogged and well-funded legal departments of any company, so that is a good reason again to stay quiet. Yes, the PageRank algorithm is publicly known, but Google’s search engine algorithms, in practice, are way more complicated than that, such as the application of ranking penalties.
Few companies has attracted more scrutiny online by smart people than Renaissance Technologies, which oversees the famous and record-setting Medallion fund, which for the past 30 years has beaten every other hedge fund in existence in returns. A Google search shows again hundreds of posts and discussion, such as on Quora and Hacker News, inquiring about the strategy Medallion uses, and after three decades and hundreds of employees, no one is any closer to understanding how Medallion works beyond some vague ‘statistical methods,’ which is next to useless. Sure, some former Renaissance employees may have leaked pieces of the strategy to competing hedge funds, but still, no one is any closer to understanding it beyond just speculation. Renaissance’s compensation is also a secret, but it’s reasonable to assume it’s a lot.
So this is just three examples of organizations which combined employ a lot of people that have been able to keep trade secrets or procedural policies secret for a very long time.
Another example is “stealth” technology, that was kept fully secret until some vague renderings were officially released in 1988, despite many thousands working on it.