Working under a car on axel stands was what made me get the lift as, as the older I got the less confident I became. Following the basic checks on my lift gives me 100% confidence to get under a car and wrangle it with no signs of any chance of failure. If a 4 post falls over, it would normally be down to user error, taking shorts cuts or rushing. There was three of us working on the Corvette, not counting dogs and each time it went up or down, we all checked everything was clear, dogs were safe, no one was leaning on one of the posts chatting etc..
That being said, the installers or as I like to call them - lazy bastards convinced me it didn't need bolting to the floor and I said, ok fine.. The first time I used it the posts all moved however slightly but it threw the whole thing outta whack. I then bolted it down myself and squared it up as it should be.