Summary
Without some form of logical organization of users within your network environment, chaos reigns and administration grinds to a halt. Administrators need some way to lasso groups of users together into logically identifiable groupings so that changes, security privileges, and administration can be accomplished en masse. Active Directory was specifically designed to be extremely scalable in regards to administrative functionality, and the flexibility of OU and group design is a testament to this strength. Proper design of both organizational unit and group structure will go a long way toward helping you gain control and reduce overhead in your domain environment.