Earlier quoted context omitted.
Microsoft has a history of being hostile to the open-source and free-software communities. They release "shared source" code under licenses with onerous terms or encumbered with patents. In the event that an open-source project built on their technology becomes popular, Microsoft attempts to smother it (for example, see their treatment of Mono). I trust Google about as much as I trust Red Hat, Canonical, or any other…
I agree that Microsoft hasn't been trustworthy historically, but how have they smothered Mono? And a counter-example is Samba.
Samba benefited from Microsoft's documentation because Microsoft was forced to disclose it by court order.