Yep - a few years back on AWDC Comp on Salisbury Plain. In was the Simmonite sisters. The drive flange failed and the outward movement of the disc just tore the caliper in two. Left a wheel, hub, disk and half shaft rolling down the hill as one, with a hobbled Simmbughini limping off in t'other direction. Ended their day.
Don't quite think it was the failure in this case, though!
cheers
8)
Eeyore