I was raised to send thank you notes for just about everything, particularly job interviews. So last year I was prepared to send out thank you notes for interviews until I read on this forum that it really isn't done nor necessary. Sites just assume if you're going to bother going to the interview that you appreciate the interview, no thanks needed. When they rank you, they're not going to check off a check mark for having received a thank you. However, the site I'm currently at is a consortium with 4 sites. I interviewed at all 4 sites and one interviewer in particular made a point of giving me her business card and telling me that should I have any questions, please feel free to contact her. So in light of her going the extra mile to make me feel "wanted" I felt I should send her a thank you. I did and she actually responded back to my thank you telling me how much she enjoyed meeting me etc. I did not send thank you notes for the other interviews at that site or anywhere else I interviewed. So in my opinion, if someone shows particular interest in you, then I would send a personal thank you, otherwise I do not think that sites expect thank you's.