I love the feature to allow the Group Administrator designation; however, it would be nice to be able to add group administration at the sub-group level, as well.
Because of the structure, you may have the top-level with a very senior person who wouldn't at all be appropriate to take that role. That leaves you with a person in one of the lower groups who would then administrate for all of those groups. That would give visibility that would be at too great a level.
Case in point: We have an HR Group, with three sub-groups. Those three sub-groups have various responsibilities which need to be segregated for employee protection.
There is a related issue, that needs to be addressed. Currently, when adding the group administrator at the highest level (which is the only option), it still doesn't automatically give them visibility into all of the work for the sub-groups. They have to be added manually. I currently have that listed as a product error, Request # 1137107.