Ugg, that is scary stuff. Also, make sure they are LOCKING jack stands. I was once using the non locking (perhaps double lock is the right word) and had one fail because it got tapped. Luckily it was not holding up a car, but just a corner of my camper.
Well... with the Harbor Freight recall (parts one and two); it's hard to have absolute faith in jack stands now. I saved this photo from another thread. I like the idea.