Why do so many people think Apollo 11 was fake?

Scores of people around the world believe the landings were staged by Nasa to boost America's prestige on a global scale, while many claim they never happened at all. One of the more popular theories suggests that the six landings between 1969 and 1972 were faked, and that the 12 astronauts who walked on the moon never actually stepped foot on it.
 This week marks five decades since man first landed on the moon - take a look at the conspiracy theories that many still believe to this day.