Things can be designed with large enough safety margins that "unlikely but possible" is effectively "never going to happen." If it's unlikely enough, you're up

Things can be designed with large enough safety margins that "unlikely but possible" is effectively "never going to happen." If it's unlikely enough, you're up in "electrons could quantum tunnel through the insulation and electrocute someone" territory. It could happen, but I'm pretty comfortable assuming that it won't. For an example in a similar vein, power grids send electricity around at voltages that are well outside what the wiring in your house (or anything plugged into it) is designed to handle. The primary side of a distribution transformer (the cylinders you see on utility poles) is something like 13,000-25,000 volts. I've never heard of that getting shorted into the secondary side with 25 kV being put into the residential power system. If you look at the teardown/comparison between genuine and counterfeit power supplies (linked in other comment), I'd absolutely believe that with a large number of those adapters in use it would eventually kill someone. The high voltage side is poorly isolated and they went so far as including a fake grounding pin that isn't even connected to ground. But a well designed switching power supply is designed to not kill you. It's scary to think that some people have these counterfeits and don't realize it's not a genuine power cord. That's the real risk here that needs to be dealt with.