My wife's Skoda has a touch screen display that says "Loading user profile". Until it has done so none of the other features are available such as Sat Nav, Audio etc. Sometimes it hangs meaning you have no audio for the entire journey.
I have never once thought "thank God someone added this feature to the car". Rather more Anglo Saxon phrases have been uttered cursing its inventor unto the 7th generation.
When I started looking at Big Data one of the examples given was of a city getting people to install an app on their phones that would track the time and location when a driver hit a pothole. The goal was to prioritise the mending of the roads in areas where the roads were used the most. To me this is a good use of sensors in cars and demonstrates a positive side to sharing data.
For young drivers in the UK you can get insurance policies that require you to have a black box fitted. These will measure your driving and adjust your premium if the evidence shows you habitually break the speed limit or drive badly. There is a definite financial benefit to the consumer from installing such a system. Where it causes problems is where the speed limit differs between the app and real world. With the introduction of the 20mph speed limit on all urban routes in Wales, some roads were miscategorised in the app database leading to people being unfairly identified as bad drivers. This gives a whole new meaning to insurance companies welshing on their bets