Straight from the Info Center;
The Job control (*JOBCTL) special authority allows a user to change the priority of jobs and of printing, end a job before it has finished, or delete output before it has printed. *JOBCTL special authority can also give a user access to confidential spooled output, if output queues are specified OPRCTL(*YES).
Risks: A user who abuses *JOBCTL special authority can cause negative effect on individual jobs and on overall system performance.
This should start the discussion,