Still, plenty of ways for someone to cause lots of damage.
One could, say, place these cables in a Starbucks, or McDonalds(two places, with USB outlets). Wait for an unsuspecting customer to come in and plug a MacBook or iPhone in to charge, now as long as the attacker is within 300 feet of these computers(like, he's waiting outside in a car), he just has to install a remote-access exploit onto the computer, now he doesn't have to be "in the same room with it", he could be in another country, and still gain access.
So, he only needs physical access, and being in the same room, for long enough for an unsuspecting person to plug in a USB cable(presumably thinking it's going to charge the device).
Or, one could just as easily stash a few of these in a pocket, and go to any store, place these on the shelves, next to the legit ones(they would have to be modeled after aftermarket cables though), and next thing you know, an unsuspecting customer comes in and buys a cable, get's an exploited one, and now, his computer can be exploited.
Hah, many public places like waiting rooms have USB charging stations, simply plug a cable in to this station, and sit back and wait for someone to plug a device in.