I've seen some pretty convincing expressions of emotions from actors who were obviously not at the time, in love, in pain, in anger etc. I'm pretty certain that any system that takes your facial appearance and no other information (e.g. you are an actor, you are currently on a movie set), it would have no way to distinguish genuine from false emotion.
If we are talking about professional actors trying to trick the tracker, then yes, it should be pretty hard to design software to overcome it. But most people aren't that good, and although they can mislead their friends or collegues, they still leave clues to detect a fake emotion. If you are interested, Paul Ekman has quite a lot of literature on the topic, e.g. see [1].
But humans are notoriously bad at picking up on details, and things like music and scenery can have a big impact on our perceptions. I'm not saying that you're wrong, I'm just saying that in the absence of any evidence to the contrary I don't think we can just assume that you're right.
