I'm working on a theory around how many conspiracy theories a reasonable person is allowed to buy in to in their lifetime while still being completely normal. My current thought is you're allowed at least 3 during your teenage years, and then one every 5 - 10 years after.
When I say conspiracy theories, I will mention that I'm only including ones that do not actually change your daily life in a significant way.
Conspiracy theories in general are a fantastic study of selective data interpretation. All of them do it in different ways, but there are some general themes. One of them was illustrated quite entertainingly by xkcd.com this morning: