Capturing Unsubscribe Reasons

We are wondering how other organisations are using Tessitura to capture the reasons a customer provides when they unsubscribe from email communications.

We are looking at setting up CSI's  to capture the information however are wondering whether anyone is using service interceptors to automatically trigger the CSI's? Have you made it mandatory for the contact centre and box office to capture this information as well as the web? 

We would love to hear what others are doing in this area.