Anecdotally, yes, it happened to me. An older extension spring setup where each end of the spring had a J-shape hook. The hook itself sheared off of the body of the spring and shot a ~2 inch steel boomerang across the garage. Fortunately my only injury was psychological and temporary.

The replacement spring was constructed differently, with the "hook" portion replaced by two complete loops of metal. The safety cable runs through that and would hold it back during a similar failure.