I once did a service change and was about to finish the job. I knealt down to label the panel, and recieved a "tingle" from somewhere. I got my meter out and checked the voltage to "ground" (literal earth) and recieved a reading of 117 volts. After troubleshooting I found an old furnace under the house that had been replaced by a heat pump system, but was not properly disconnected. It had "frayed wires" supplying it and it was touching the fuel oil line that was going to the tank located underground at the electrical meter location. The homeowner said his children were in a "kiddi pool" and kept complaining the water felt funny. He felt the water and could feel a tingle. Rather than reporting it to someone, he just moved the pool farther from the house. Thankfully no one was hurt and I disconnected the old furnace under the house. The bonding grid may have come in handy here, but again you can't prevent "dumb" people from doing dumb things. You always have that potential of hazard when someone does not do their job correctly. I still have the photo of the readings I got on my screen saver with my other family photos.
