In his book Inside Apple, Adam Lashinsky writes about Apple's extreme secrecy -- both external (not letting the media know what it's working on), and internal -- not letting people inside the company know what other people and other teams are working on. As Lashinsky explains it in an interview,
Apple people below a certain level -- and that level is a very high level -- do not multitask. You have a project, you work on that project, you know what your function is.... Apple operates on a need-to-know basis. So if you're not involved in a project, you're not involved, it's not of your business, and you're encouraged to mind your own business... You work on the discrete task that you've been assigned to work on. They don't get distracted by what other people are working on.
It strikes me that Apple is engaging in a form of information 5S -- except that in this case, the "sorting" of information is externally imposed and enforced by the company. And there are real benefits to it: you're better able to focus on your work because you're not getting buried by a bunch of needless "reply all" emails, or getting roped into meetings that are only tangentially -- at best -- related to your work. By identifying the important and relevant information for each person, and by defining clearly focused responsibilities, Apple eliminates the needless cognitive load on people.
That's certainly a contributing factor that enables them to do their best work. I'm certainly not advocating that all companies follow this route. (Neither is Lashinksy, for that matter.) But it's worth considering how much unnecessary cognitive load you impose upon your people in an attempt to "keep them in the loop."