A large financial services company I have assisted has an HR representative interview all lawyers who leave the department. The notes taken during those structured interviews can turn up some opportunities for improving how the department runs.
People who leave may speak honestly, constructively, and objectively, especially if they are leaving on good terms and wish the department well. Or, people may be harshly critical, especially if they were terminated for poor performance or otherwise involuntarily. Either way, a thoughtful manager can sift through the interview notes and perhaps pick up a nugget or two. (See my post of June 15, 2005 regarding the costs of turnover.)