@Johannes
I believe you're missing two key points in your discussion. First, Forbes target audience will be middle to upper-class who will own or drive one of these newer model vehicles and potentially utilize services where they regularly give others access to their car (valet, cleaning, etc). Second, just like a server back door exploit you described in this same podcast, this service could leave the reprogrammed dongle for someone else to unlock the door, start the engine and be on their way much later (hours to weeks) which would keep the car owner from linking the two events in their mind.

Another thing you can do with that port, without even having to leave the dongle connected permanently, is program additional remote keyfobs that can be used to unlock the car doors in the future. I recently had one of these keyfobs fail, and watched the mechanic connect his computer to that port in order to program the car to accept the replacement keyfob. So physical access to the interior of your car with access to that port is a no-win scenario, basically. If you've ever let a valet park your car, it could be 0wned already.