At a past consulting job the CEO claimed Google was reading his confidential information in the 00’s and refuses to use anything except Office 365. In his case confidence that MS will not act improperly is the most important feature.
As an engineer working on Docs and related products from inception through 2010: I would be astonished if this were the case. Had such behavior become known within the engineering team, there would likely have been an uprising. There was no backdoor mechanism for looking documents, at least on the Docs (word processing) side, and in any case this sort of thing Was Not Done. My guess is that things are locked down even more tightly now.
I use Docs all the time. It's really nice to hear privacy is important to the team!
Interesting. You would think the case of Alex Kibkalo would lead to the opposite conclusion. Microsoft prosecuted a blogger for piracy of Windows software after reading his private hotmail emails.