Some stories my dad has told:
Back in the late '70s, when he worked at an Import place(they worked on Fiats, Alfa Romeos, Saabs, etc.), one of the other mechanics drove an old Fiat in and got the lift ready. He hit the button and then just kinda didn't pay attention, till he heard some noises, then looked over to see the wheels on the ground and the seats pushing up on the roof of the car.
Other stories of cars coming in, going out, and coming back the next day on a truck, happen every so often.
Also stories of MPVs and B-Series trucks being put on the lifts and hitting the roof of the building...
My bro also has self-screwed up his own cars, but usually not bad.
And from my early mechanical days, not really car related, but on my first multi-speed bike, a RoadMaster Razor's edge, I liked to keep the gears nice and WD-40ed, so one day I was spraying the gears down, then decided to spray the wheels because it made them nice and shiney. Got on the bike without trying the brakes, and went down my street here(a hill), and gained a ton of speed trying all the gears, then it was time to slow down. Hit the brakes, nothing happened(WD-40 workes pretty damn well as a lubricate, lol). With all my hand strength I gripped the brakes and nothing, then the WD-40 wore off, and I locked both tires and flipped off the bike, luckily I wasn't really hurt...the bike was fine too, but there were chunks of the brake pads stuck on the wheels.
Hehe.