How is it that Facebook ads play right before the climax or high point of any video. Just when I'm interested to see what happens next, bam, like clock work, an ad pops up. It does not seem to be a fixed time, but more to do with the specific content of the video. Is it just me or is there some sinister algorithm at work that can detect the moment in a video the viewer will be most interested? so the viewer will have no choice but to sit through the advert to see what happens next. Or is the timing of the ad predetermined by some other means ?