They are rampant though. Been in the medical system for the better part of a decade and after every hospital visit, I have to call the hospital to verify each bill I receive. At least 20% of the bills mailed to me are fake.
Another +1 on soliciting feedback from teammates on a regular basis. As long as the manager is impartial, doesn't take sides, respects privacy, etc this can benefit both the subordinates and team. Grievances get aired and steps can be taken immediately instead of hearing about issues in the subordinates' peer reviews at the end of the year.