I often go to the cinema, see the trailers and think 'that looks like it could be a good film to watch', and then watch the 2hr+ film. When leaving the cinema and chatting with my whomever I went to the film with, we struggle to remember all of the trailers we saw. Sometime vaguely remembering that there were some you liked the look of.

Cinema chains should put on their website a way to see what trailers showed before the films of the past week to both let you remember what you saw, but also allow you to flag them as a "let me know when this is released." notification service.