LOL The worst thing ever, in my opinion, is the BOW FLEX.
Sean
You're using the leg press machine as a calf machine; you're not really putting the bulk of the pressure on your back in the same way as if you were lowering the weights in a leg press.
And, as your friend's case proves, a Smith machine isn't a guarantee against injury. You still have to use good technique, and know how to use the machine. And -- like any machine -- it can fail to work properly!