Somewhat related story: me and some coworkers were talking in a room where someone had a Windows 10 laptop being used to present some data. We were talking as usual when the laptop suddenly decides to open a browser to a Bing search with what looked like a few (badly) voice-recognised words of our conversation. That was a rather awkward moment, given that we were discussing some extremely confidential information, and not helped by the "did someone say 'Hey Cortana'?" the laptop's owner promptly blurted out. If I remember correctly, none of us said anything that sounded remotely like that phrase, yet it activated.

It's now company policy that built-in microphones have to be disabled, and only external ones are allowed to be used when necessary.