As to spine degradation, I think 95% of the confusion comes from a person not being careful to measure spine at the same place every time on an arrow.
I've seen up to .025" variation in deflection around the axis of a single carbon shaft, but I didn't know there was any confusion on this. Jeff, Len and I - along with others - have both discussed carbons' spine inconsistency around the axis of the shaft and the desireability of matching up the spines before fletching - in other words, placing the cock feather on the axis with the stiffest deflection reading.
Of course, one must have a spine tester to do that.
Most guys don't have a spine tester to check their arrows anyway. The only thing they can go by is how well their arrows group. And as their arrows degrade slowly, their groups slowly get bigger until one day they notice they're not shooting as well as they did before.
Since so many people have spouted the "carbons are either straight or broken" BS, and it has been repeated over and over again, it has become 'truth' with no absolutely NO basis in fact. Listening to that crap, one would get the totally false impression that carbon arrows never bend, never wear out, never change at all.
So, the poor guys don't attribute their poor groups to the arrows. As a result, they start changing the tune on their bows and trying new releases, new shooting styles, all kinds of things. And none of it will do a bit of good until they buy a dozen new arrows to replace the worn out junkers they've been shooting the past 6 months.
Guys like treetop3, who have their clinkers just jump right out there and grab their attention, are lucky. In their case, it's immediately evident the problem is the arrows and not their bow, form, release, etc.