I agree with both of the previous answers, and am highly suspicious of hierarchy, but will offer a possible (highly situatinal) defense of what might be argued is hierarchical decision making.
Because hierarchical decision making can in fact be more efficient in situations where time ind decisiveness are important, it can serve as a temporary (and willingly agreed upon) model for things like animal liberations (should that be the sort of thing one does - I have seen this argument put forward in ALF literature, which is why I thought of that example) where there is a particular shared goal, and speed and focus are important. This presumes some previous degree of comfort and trust among the participants, who all would've willingly chosen to be involved in said action, and would've also then consented to this structure, for the duration.
I would assume that up to the point of the actual action, all voices would be equal, otherwise there is an extremely unhealthy dynamic at work in the group with the beginnings of an expert vs. layman sort of situation that any anarchist should be extremely wary of.
I think it could be argued the example I gave is not actually hierarchical, as there was choice throughout, and there are no real formal consequences to choosing to break with the agreement at any time, as well as the temporality of it, but it at least muddies the waters a little.