Character mistake: When Mary is in the execution chamber, about to be incinerated, there is a voice over of the countdown till her death. They count back from 9 seconds and say 8 seconds, 7 seconds, 6 seconds, etc. The count is too slow. Every time they say a second, it's actually two seconds having passed. (01:22:10)
Character mistake: The red ribbon with Mary's scent. Preston always holds it in his right hand and keeps it in his right pocket. However, Yurig (the leader of the Underground), during Preston's low detector test where the Resistance is ensuring that Person really has begun to feel human emotions, Yurig says: "you carry a ribbon with her scent in your left pocket. You smell it sometimes when you think no-one is watching...etc." But it was never in his left pocket, always in his right.
Answer: Because of their display of emotions it is clear that the elite are not taking their Prozium. If the idea of the emotionless society worked, then yes the elite should be taking their Prozium. However, this society obviously doesn't work and instead of being the solution to all man's problems, Prozium have just become a way of subduing the masses while the elite are free to do as they please.
Andreas[DK]