I'd like to consider having bounty separated, to some degree, from the accepted answer.
It would work something like this:
Oh gee, I'm indecisive, and all these answers are so scrumptious! I want to eat them all!
Well... I'll choose this one as the official answer, and they'll get the full bounty.
But these other four are nearly as good, and they should be rewarded for answering my call as well. I will give them the same award from my own rep.
So if I offered a 150 point bounty, the first person would be accepted as the answer and go to the top, and receive the original 150 rep (100 from me, 50 from the system).
The next four would each receive 150 rep as well, from my rep.
It would cost me 750 rep to do so. Other than the accepted answer, nothing else would change in the question.