I guess it could be your personal preference, but to have the proper weight of the arrow for the proper spine flex is important from what I have been reading on bow tuning.
By looking at the Easton bow tuning chart, it tells me that if your spine flex is too stiff you could be hitting too far to one side, and the opposite side if it is not stiff enough.
I am no expert, but the amout of weight that I have on the front of my shaft has to influence the flex of my shaft to some extent.
If there is someone out there who can verify or deny this, I would love to hear from you.