There is an old apartment house across the street from a certain campus. It used to be operated as part of the dorm. It has a large shingle labeling it as the "Hafner House." Several electrical engineers, including two of my college professors, used to live there together as students when they were in college years ago.
The story goes that someone had turned the bathtub into a shower with one of those hose attachments. A mirror was also installed on the wall above the tub. One of the guys was up late studying for a test and decided to take a shower. While in the bathroom, he bumped his arm against the metal bracket that held the mirror onto the wall. He got a shock. Startled, he finished his shower and stayed awake studying for the exam. Being a house full of electrical engineers, it didn't take long before they all broke out the multimeters to satisfy their curiosity. They found that they could get 50 volts just between the tub drain and the plaster wall, I think it was. At least in those days, you were lucky if Plant Service would fix anything; if an appliance broke in an apartment, then that was just tough luck. In the morning, they called Plant Service saying, "Hey, we just about got electrocuted here," and Plant Service was over almost instantly. It turns out that the house had knob-and-tube wiring still in service. All those long showers had soaked through the plaster and the cloth insulation on the wire, forming a conductive path. But it gets worse. How do you think they fixed it? They got some of that plastic paneling like you see in kitchens and restrooms which is easy to clean and covered the wall.
There's more. Once when one of the guys was washing dishes in the kitchen sink, he reached up to pull the chain to turn the light on, with the other hand still in the water. You can guess what happened. He suffered no permanent damage. They called Plant Service once again to say that they'd almost been electrocuted. Again, Plant Service was there within the hour. It turns out that here, the chain was mechanically and electrically connected to the switch on the hot side, but the switch was in the neutral line so the voltage was coming through the bulb when the switch was open. The engineers had great joy demonstrating to Plant Service how they could turn the bulb on by connecting a jumper wire between the pullchain and the sink. Now, to effectively reduce the shock hazard they could have turned the switch around, replaced the switch, wired it correctly, etc. Do you want to guess how they fixed it this time? They put a plastic link in the pullchain. After that they were safe except that when they operated the pullchain, the plastic link and a little bit of the hot chain would come out.
I believe that this story is true as it was told to me, as I have remembered it, and as I have written it. In fairness, I think I should say I also believe that these things have been fixed correctly since then. The Hafner House still stands.