Conspiracy theories appear whenever something of such big import occurs, whether its a terrorist attack or a historical occurance like the moon landing. We will never know if it was an inside job, disinformation makes damn sure of that.

Skepticism is good, however too many 'skeptics' do not apply the same degree of skepticism to their (contradictory) pet theories that they apply to others (just like people don't apply the same level of skepticism to their religion that they do to others)