I may have mentioned some of this in an earlier blog post, but I find it very interesting how strikingly similar conspiracy theories are to religions. They may not be theistic religions and they may not deal with the supernatural, but otherwise they present most of the same phenomena that religions do.
Many of the people who have converted into them feel the urge to convert others, which is extremely typical of religion. In fact, in some places (especially the United States) conspiracy theorists are more organized, louder and more intrusive than most religions are. They will preach to people on the streets, distribute pamphlets, books and videos, they will go on radio and TV shows, they will organize protests, marches, ad campaigns and so on. They are also strikingly similar to creationists in how they present their arguments, the kinds of argumentative fallacies they use, and what their opinions are about science and the scientific community.
In fact, creationists are not the only striking parallel. Such parallels can be found with many other extremist cults such as scientologists and some of the most extreme denominations of Christianity and other religions, such as the Westboro Baptist Church.
Individual conspiracy theorists will also show striking resemblance to the most avowed religious people. Many times when you watch them eg. on TV shows, interviews, discussion panels and so on, you can clearly see the outright fervor and passion they have for it. (One particular example was outright hilarious. It was a TV show discussing the 9/11 conspiracy theories, and the guests were two of the authors of one of the most popular "documentaries" on the subject, and two people from Popular Mechanics. While the latter two remained completely calm, collected and civil throughout the entire debate, the two conspiracy theorists had really difficult time collecting themselves. They were constantly shaking their heads and clearly showing extreme frustration, so bad in fact that they seemed to have difficulties remaining seated. You could outright see their blatant religious fervor. It was quite amusing to watch.)
It's curious how conspiracy theories seem to have gained enormous popularity during the past decade or so. Before that they were just fringe phenomena believed by an extremely small minority, who were mostly regarded as silly and deluded (if not outright lunatic) by the rest of the population. And this is not just with conspiracy theories that have popped up during the last decade. For example the Moon landing hoax theories have existed since at least the 80's but didn't gain any kind of widespread popularity until well into the 2000's.
One could say that conspiracy theories are one of the fastest-growing religions in the modern world.
I believe that the main reason for this is the popularization and wide availability of the internet, as well as the progress in technology, which has allowed basically anybody to create writings and videos and publish them for the entire world to see. Back in the 80's and long into the 90's only an extremely small portion of the population could ever hope to be able to create such a work and make it widely available. The most that people could hope to achieve was to write a book, which would then usually have a ridiculously small circulation and would mostly be forgotten.
For the past ten years or so, however, anybody can create online "books" and videos with little to no money, using free and cheap tools that were only available for the rich in the past, and with a cheap channel to distribute their work for basically the entire world (which in the past would have required enormous amounts of money.) This has therefore created an outlet for this religion to spread, causing an avalanche effect: The more people read or see about it, the more they will spread the word to others, and so on.
While conspiracy theories resemble in many regards religions, the reason why people believe in them might be slightly different. Most religions appeal to the innate beliefs that people have about their own spirituality (in other words, the instinct that most people have that their consciousness exists independent of their body, that it's separate from it, and that the body is just a conduit that the consciousness uses to interact with the physical world.) They appeal to the worry that people have about what happens to their consciousness when they die.
Conspiracy theories, on the other hand, excite peoples imaginations and their sense of self-importance. They entice people with the prospect of knowing more than others, with being part of a knowledgeable group that's "in the loop" so to speak, that know the innermost secrets of the governments and other organizations they consider shady. It's also a form of pseudointellectualism: It gives them the feeling that they have a special form of knowledge that most other people don't have. On a different tangent, conspiracy theories also appeal to the fear people have of being deceived (which is highly ironic given how deceitful conspiracy theories are.)