Well-said. Most of us do this for fun. Injuries aren't fun.
The only time I've had a jack catastrophically fail is at an autocross. The more hands you have working on a car, the more dangerous it is--especially at an event where time is short. I've seen a more close calls at crapcan races and autocross than a whole lot of weekend wrenching.
If you're working on a car as a team, take responsibility for your own safety before getting under a car. Look around.