I'm sad my second thought about this (after dismissing it as a coincidence) was that it could be used for marketing - "I randomly thought about this book/show/movie whatever, and hey what do you know? The sequel is coming out!". Basically another variation on 'organic' advertising in comments that's been around for a while.

Of course I highly doubt that's what actually happening here, but the idea is unpleasant. I hate advertising, I don't want it messing with real interactions with other humans. I'm not sure how to express the idea, it's like its so pervasive I'm thinking about it when its not even present.

This idea makes me deeply uncomfortable, and I shouldn't have included the name of the book in my original comment (now too late to edit).