Has a worst fear of yours ever come true?
I still wonder what's behind the eleventh doctors door. Himself, perhaps?
So do I, and I think that's most likely. Because honestly, what else could the Doctor be scared of? He's faced danger countless times, never losing his cool. But seeing all your faults, all at once, is enough to frighten anybody.
And they're setting up an evil doctor anyway with the doctor that was no doctor. I can't wait till the 50th anniversary special!