Mac OS X Server: Mobile accounts require a UUID
Summary
In order to create a mobile account, the user account must have a UUID (Universally Unique IDentifier, sometimes called GUID, for Globally Unique IDentifier) which identifies the user's account in a network directory service.
Products Affected
Managed Client, Mobile Accounts, Portable Home Directory Accounts, External Accounts
Directory accounts created on Mac OS X Server 10.3 or later have a UUID created by default. User accounts created in a third-party directory service may not have a UUID by default.
As of Mac OS X 10.5, UUIDs are required for user accounts in order to provide a unique identity for each user for functions like file sharing, nested group membership, file permissions and access control lists. If a user does not have a UUID, some of these functions may not work as expected.