For those of you looking for actual data on a failure. My father's Viscount fork failed. The damage was about 9 teeth, a few dozen stiches and I think even a cheak bone. At any rate, the failure was real and the injuries were real. Use with care. One note, it did creak prior to failure. Hence I hate to ride anything today that creaks - from anywhere.
The fork had an aluminum crown and a steel steerer tube. An aluminum plug joined them. The aluminum plug sheered in two. Looking at the remainder from top was interesting. It was about the diameter of a nickel. The outer 1/3 ring was a different color/texture than the inner 2/3. Clearly a stress fracture was developing slowly, and was polishing itself and causing the creaking. Until it got deep enough in that the remaining piece could no longer hold up and it broke - leaving a crisp graininess visible.
He keeps it as a souvenir, and rides a nice Trek (not bad for age 73).
Dan Kasha Providence, RI
PS I replaced my Cannondale Aluminum fork with a steel one:)