[damieng]

The amount Microsoft would have to lose - in courts and public trust - if they were to abuse the private sensitive data held in their systems - would massively outweigh any benefit they could hope to achieve from that information.

[nickpsecurity]

That's already been tested:

https://www.theguardian.com/world/2013/jul/11/microsoft-nsa-...

They're still in business. Numbers look good. They also have advertising and telemetry on paid stuff that people would usually assume doesn't sell them out like free, ad-driven services. Windows, Office, and Xbox are valuable enough that customers will tolerate quite a lot before leaving.