It's private between the occupants of the vehicle. The scenario I had in mind was an idle chat with the driver, perhaps about politics, perhaps about unionizati

It's private between the occupants of the vehicle. The scenario I had in mind was an idle chat with the driver, perhaps about politics, perhaps about unionization at Uber. What you say has not (so far) been shared with a multinational corporation. 'Private' isn't a binary - there's a huge difference between being overheard by a stranger or acquaintance, being seen walking down the street through the window by someone's grandma, and placing microphones and surveillance cameras around public places, gathering the data at some central location, to be used for ads, building a commercial or political profile of you, and subject to police seizure, or bought by private security that's investigating troublemakers at some company, or just running a background check on you before offering you a job.