I wrote them to each interviewer, including student interviewers. Also, at one school, a admissions receptionist went out of her way for me, answering questions and carting me across campus for a faculty interview. I sent her a note, too. Did it look like sucking up? Maybe. But I was sincere, and sounded like it in my note. I didn't send it to her, or the interviewers, really, not merely because it helped my chances, but because it is polite and they deserved them. Wouldn't you appreciate one if you took a day to spend with candidates?