[HLMencken]

I can't think of a specific example at the moment but so many action/heist/war movies would be examples. How often do you see a huge elaborate plot which takes so much planning or is crucial to the story and then when its pulled off, it could have been spoiled if one person would have screamed, or some other very easily possible event occurred--like people actually had peripheral vision and could easily spot someone running just out of their main field of view (every escape movie ever fits here, too).