[danielki]

Compartmentalization, as runjake mentioned below, is key.

I worked at Microsoft during the development of Windows 8 (disclaimer: I no longer work there, and only speak for myself here). Certain "secret" features were not available in the "default" OS configuration until shortly before they were announced. Access was restricted only to those who needed it, and only then with manager (or, I believe at one point, director) approval. If you had access, you were under strict instructions to only enable the features when nobody else was around.

Artifacts from this process are probably what resulted in the "workaround" in the Developer Preview build [0] to revert back to the classic start menu.

Similarly, with the Surface, much of the company was in the dark until the official announcement. Some of the lengths they went to in order to keep it secret, included only a few executives knowing and trying to avoid ordering multiple parts from the same vendor [1]. The team worked in a vault-style building where one door had to close before the other would open [2].

There's also the giant "fear of being sued or prosecuted" thing. Big companies can afford good lawyers, your average employee probably cannot. Hell, Win8 was released over 3 years ago, I no longer work at Microsoft, yet I've still gone back and triple-checked this post to make sure I'm not disclosing anything about it that's not well-known to the public.

[0] http://blogs.msdn.com/b/balsharfi/archive/2011/11/04/metro-s...

[1] http://money.cnn.com/2012/10/28/technology/mobile/microsoft-...

[2] http://www.techradar.com/news/mobile-computing/tablets/how-m...