<p>I think BES’s experience is sad, because it suggests that most thank you notes are sent strategically–in the hope that it will contribute some small admissions bump. (I think most students and parents think of the alumni interviewer as out of the loop once the report on the interview is filed.) </p>
<p>It seems to me that thanking an alumni interviewer is more obligatory than sending a note to a professional adcom, because the alum gives up their personal time to assist in the process. Seems just plain inconsiderate not to than a volunteer.</p>