We all trust our e-mail to be stored in the cloud, we store sensitive files etc on services like dropbox, we trust that our operating systems aren't collecting/sending data, etc.
You're already using and relying upon MANY services with the ability (if they really wanted to) to steal TONS of private information from you.
It all comes down to trust. But don't pretend like this opens up some new door for privacy concerns.
Ex. If Apple wanted to, they could watch us through our macbook cameras and listen to us all the time. But we trust that they don't. Same thing here.