If the role graph produced by usersInfo with the showPrivileges option exceeds the BSON document size limit, an exception is thrown.
Since usersInfo is used in the authentication process, this prevents the user from authenticating.
Currently the user and role management commands do not validate that the modifications made actually result is usable users. The worst case scenario is a userAdmin could lock themselves out.
There should be some manner of warning or error when this occurs.