Better late than never:
Recently, I've worked on a document to describe when it is necessary for a user to have administrator rights in bugzilla.wikimedia.org. It affects a small number of Bugzilla users (less than 30) who were contacted via email while drafting the policy.
The policy can be found at https://wikimediafoundation.org/wiki/Bugzilla_administrator_rights_policy
It was written in order to explain why a specific user needs to be an administrator (or why it might not be needed).
Following the principle of least privilege, Bugzilla administrator rights are only required for a small number of rather uncommon tasks, with the one exception being editing Bugzilla user rights (if you want to know more: these tasks are also listed in the policy).
A combination of other, more specific Bugzilla rights very often allows executing the same tasks, so nobody will lose any ability to perform tasks in Bugzilla that s/he could also perform before.
As usual, a list of current Bugzilla administrators can be found at https://meta.wikimedia.org/wiki/System_administrators#List
I'm happy to answer any questions that may arise (and that were not already answered in http://lists.wikimedia.org/pipermail/wikitech-l/2013-June/070062.html ).
Thanks, andre