Broken steer tube.From http://www.flickr.com/photos/huggerindustries/3056298980/in/photostream/ as of 2008/12.
This racer rode through the ditch before the run up and his bike snapped in 1/2. Wasn't hurt, the crowd cheered, and a damn good (albeit expensive) story to tell.
Update: he bunny hopped into the ditch.
[T]he extended story was that he attempted to bunny hop the ditch before the run up and landed mid ditch . . . I don't know that any fork would've survived that; would've at least bent or another part would've broke.
It is typically desirable if parts fail by crumpling rather than snapping.
The fork is carbon fiber so the steer tube is likely either aluminum or carbon fiber.
See also FAIL-119.html.