After getting killed in hardcore mode and play as spectator, everything disappears.
Is it a glitch?
My videos: https://www.youtube.com/user/robingravel
My cartoons: http://www.dailymotion.com/robin-gravel
Flash Animation (if your computer supports flash):
Few flash movies have easter egg/extras
Not quite everything, I can see a few deep caves but only from under the world, if I go back up over the bedrock it disappears again.
So, yes, same result here.