It would be nice to have a feature like the community suggesting the difficulty of a question, and based on that the rep awarded to the answer would be added by a plus X based on difficulty.
That would increase the chance of difficult questions being answered.
It would be something like,
(1) User(s) voted this question as Hard
(5) User(s) voted this question as Medium
(0) User(s) voted this question as Easy
(0) User(s) voted this question as Subjective
Maybe SO could use this to balance the questions attention.
IMO(In My Opinion): Voting as it is today, only determines community preference for questions.
OBS: This could also be used for custom searching questions.