They do have privacy policies which say they won't sell that data, or use it for advertising or anything other than delivering the service. But - who knows if that is true? There's no oversight. And if they get caught breaking that privacy policy, who has the appetite these days to do anything meaningful in terms penalties? Nobody.
> who knows if that is true? There's no oversight
The oversight is that those companies rely heavily on being trustworthy, and proving untrustworthy would be disastrous for their business models. Companies don't have to care right now because they have reason to believe Google, MS, et. al. aren't sniffing that data. If they came to believe they were?
Google alone is making $43 billion on Cloud and would prefer not to jeopardize that revenue stream.
The reason why this does not result in a significant loss of usage is because trustworthiness-usage is not a linear function or a even a continuous function -- it is a step function. To cause less usage, the loss-of-trust force has to be higher than the networking effect force. Otherwise, behavior does not change.
That's what I don't get - security and compliance people are paranoid.
This is the kind of thing they shouldn't be requiring evidence to care about, given the rest of their job is about the "what-ifs". Just seems crazy to me.