There are other scenarios. Apparently (I do not own a car, so forgive my ignorance), it is possible now (at least above a certain price) to unlock your car remotely via smartphone or something. Imagine a criminial organization gaining access to a car manufacturer's network so they can steal cars.
Some people apparently like the idea of being able to lock/unlock the front doors of their houses/apartments via smartphone app. I am not certain how this is more convenient than getting a key out of your pocket, but it doesn't matter - the same scenario applies. These are probably going to be "cloud"-based, so if someone can compromise the servers, they can now gain access to entire neighborhoods. (Or, alternatively, lock the doors, keep the people inside.)
Some people apparently like the idea of being able to lock/unlock the front doors of their houses/apartments via smartphone app. I am not certain how this is more convenient than getting a key out of your pocket, but it doesn't matter - the same scenario applies. These are probably going to be "cloud"-based, so if someone can compromise the servers, they can now gain access to entire neighborhoods. (Or, alternatively, lock the doors, keep the people inside.)