The gist of the talk (and the notes) is that people routinely overestimate the risks of transparency and undervalue the benefits of openness. It’s a hard habit to break. We assume that increased control will lead to increased security. But there are situations where the reverse is true.
Psychologists have done this experiment. The cookie lying out in the open is the most secure. Everyone can see if it’s missing or if someone took a bite out of it. If one of the kids takes it all the others will know — and at least one will probably tattle. Only if all the children work together can they get the cookie and get away with it. That requires the children to work together closely and divide the spoils fairly.
The cookie in the jar is actually less secure because any one of the children might be able to sneak it without the others knowing. (And now you know why most jars of candy are clear glass or plastic!)
Security is often the first concern raised by organizations implementing collaboration tools. But openness can actually lead to better security.