It's not without problems, sure we will be more vulnerable to somebody attacking the datastores keeping these locations. But honestly, so much data is stored about us already, this is not a bit enough leap to provoke a big outrage. It's just another piece of the monitoring puzzle, and a small piece at that. When I check my iPhone for apps using location service, I find ones that shouldn't need it, like "cut the rope", "dropbox" and "HuffPost". I also find services that really need my location to add value, like AirBnB and Tripit. When we start sharing our location, we get access to new services that can help our lives and we also expose our selves. If you don't think location services can add value to your life, buy another car and disable location sharing in your phone. If you do like the services that enhance your life with location services, enable it and learn to live with the fact that somebody might be able to figure out your movement habits. It's a tradeoff like everything in security.
...the database of their own RSS feed webserver? By picking up the current location at the various times someone's car hits your server on that morning commute just mentioned, you could probably map out the commute in detail within a few weeks.
No need to map it out, as the LEAF provides the current or last navigation destination lat/lon in the request as well! Most LEAF drivers will probably have something programmed in, as the car provides range information and traffic re-routing functions based on destination.
