By default, all users are created with access to all devices. It would make much more sense to be able to assgin user 'roles' specific tags so that a user created with 'read only' access for instance only has access to specific tags. I see two scenarios that would be extremely useful:
1. Tie user roles to default tags
2. Change default tags for users without tags assigned
These options would greatly help to reduce the administration time involved with setting up new users and would provide a lot of flexibility.,