Question from Ed: Is there an Administrator hierarchy? Who can remove/bestow admin powers?
Jason answers: Leopard and Snow Leopard have four types of user accounts: Administrator, Standard, Managed, and Sharing Only. The only account that can remove or bestow admin powers is the Administrator account.
The Administrator account can create, delete, and modify any account, install software in the /Applications folder, and change system settings. Standard accounts cannot administer other accounts, they can install software in their own account folder and change settings related to their accounts (like their desktop picture). The Managed account can have parental controls set up by an Administrator account. Some of the restrictions that can be applied are inappropriate Internet content, the amount of computer use, and access to applications, email, or iChat. Finally, Sharing only account users have remote access for file sharing only.
If you were to put them in a hierarchy from most powerful to least powerful: Administrator, Standard, Managed, Sharing Only.