The June 12 release of Canvas Commons (Commons Release Notes (2016-06-12) replaced the previous subaccount-based sharing permissions structure with a new "Groups" model. These Groups require manual management, either by a campus administrator or an individual designated as a Group Manager.
The previous subaccount-based sharing model allowed instructors to more dynamically share resources with their departmental colleagues without any need to identify and individually designate each one as a group member. At an institution as large as ours, with over 40,000 active Canvas users, manually managing groups quickly becomes an unsustainable process.
Although the new groups model provides some useful ways to support cross-departmental collaboration and resource sharing, removing the ability to dynamically restrict access to Commons resources by subaccount is overall a significant downgrade to Commons' usability and functionality. The subaccount-level sharing should be reinstated, complementing the new option to manually create and manage Commons groups.