That's an excellent question. I think exit interviews are invaluable not only for gathering real information about employee perspectives that affect the company's productivity, but also as a last opportunity to head off legal troubles. I think the key is 1) to assure the employee that their job references will not be negatively affected, and 2) to sound like the company genuinely wants to know what the employee has to say. So the person conducting the interview has to be high enough mangerially to affect policy, but removed from the supervisory line of the employee. I would even go so far as to offer a written reference up front, in addition to specific references in the future. That lessons the employee's fear that something negative will be said, because they already know exactly what they should be able to expect in the form of a reference.

__________________
Aatish Parker
Always speak the truth
People Law