It's not as bad as Amazon, apparently. I've known people there who say everything is compartmentalized. At Microsoft, it's typically only the bleeding edge stuff they keep secret internally.
Keeping things secret is only a part of the problem. Corporate utter forgetfulness of the past is another. Consider the tale related by Stephen Walli (referenced at https://news.ycombinator.com/item?id=11560510) about the Microsoft people who didn't even know that Microsoft had the SFUA/SUA with Windows NT.
> "I had to explain to the [Windows High Performance Computing team] that they already owned the technology they needed, but to no avail. They couldn't get their head around the idea."
> "I had to explain to the [Windows High Performance Computing team] that they already owned the technology they needed, but to no avail. They couldn't get their head around the idea."