I'm all for using dashcams, but the data should not leave the vehicle unless the owner intends it to (or a warrant is issued).
As for the data not leaving the dashcam it won't at first because internet connectivity is still spotty and expensive, eventually it will probably stream it live to you insurer which will perform some analysis on it to see how you drive in order to define your premiums, so if you speed you get to pay more. It won't surprise me if insurers don't already have access to some telemetry from cars (e.g. the one which is downloaded during routine checkups) that can be used to extrapolate your driving behavior for example how often you break suddenly/emergency break, most modern cars come with accelerometers today to ensure that air-bags deploy properly even when the is hit from the rear or the side that data is probably stored in the control box.