Maybe I'm jaded, but given Microsoft's history, it's unclear why anyone would ever trust them, regardless of what they say or do publicly.
https://en.wikipedia.org/wiki/Windows_10#Privacy_and_data_co...
or:
https://en.wikipedia.org/wiki/Skype#Security_and_privacy
(I agree that it is good that Microsoft makes this move now.)
Microsoft has simply discovered that a previous business strategy - monopolistic embrace, extend and extinguish-is no longer a good one in today's open, networked world. Hence they have moved to new strategies which are more palatable to the tech community. Slightly late, but still in time to remain relevant.
Mostly, I'm referring to Ballmer.