I had an electrical sub-contractor using a backhoe punch through a 21" high-pressure water line. By the time the water was shut off, 2.4 million gallons of water created a lake at a busy intersection. The 60'+ geyser was cool looking.
My neighbor was installing a fence along our property line last fall and hit my gas line. The sad thing was, he never told me about it. I came home that evening, sat around the house smoking a cigarette, and then received a call from my OTHER neighbor warning me...
Did you see the aftermath? A few years ago a gas well was being drilled just a few houses from where I live. I loved that thing and visited it often. Really cool.
The best part was when they were burning the well following a fitting with a valve to see how long the gas would burn and how good the quality of the burn was. That things burned for days and sounded like a jet engine in the woods.
...or that the workers operating the digging equipment will pay attention to the markings. We've had clearly identified cable conduits ruptured several times by operators just not paying attention -- one was even in an area where the construction foreman had workers hand digging around the conduit. Some new guy comes in with a backhoe while the foreman is elsewhere onsite, and bye-bye conduit (including all the private fiber and copper cable contained within).
Another time a street repaving crew piled dirt on the Ms. Dig markings, then proceeded to hit our building entrance conduit because "it wasn't marked".
When I was in Junior High in 1978 (Lacey, WA) a guy tried a Y-Turn in a parking lot, and backed into a propane tank, blowing up the entire propane station, killing the driver and everyone inside. My school bus was about a hundred yards up the road and we could feel the heat.