Logic dictates that in grizzly country, EVERY member of the party needs to carry their own bear spray. It's not a bad idea for Black Bear country either, but admittedly, the risk of encountering an aggressive black bear is far less than for a grizzly.
Why all that redundancy instead of having only a few carry spray, you ask? Whatever happened to sharing gear weight?
Well first, the group is not always going to be together. Individuals will separate from the group for various reasons at various times, and even if they don't go far or for long, they are away from the relative safety of numbers and so being vulnerable, need their own protection.
Second, in the case of an incident - like this one - where there apparently was not time for the lead hiker to draw his spray (even if he had had it), at least one or more of the others would have and could use it to deter the attack.
Third, No battle plan ever survives first contact with the enemy. Someone always seems to fail to "get the memo" - in this case, to keep their spray handy AT ALL TIMES - and just stuffs it someplace where they can't get at it in time when it's needed.
It's your a$$; cover it the way you want. But if you're going with me, you'll carry bear spray, just like me.
We can debate ad nauseum about the probable effectiveness of properly utilized bear spray in detering an attack, but the fact remains that bear spray not carried or not available will NOT be used and will absolutely, positively NOT deter anything