Let me start out by saying that I am a Marketing Major. "Advertising Management" to be more specific. This tends to be more of a controversial major and subject because it often has so many negative connotations. For instance, it is true that many of the downfalls of American media and entertainment are directly due to their marketing and promotions. Women strive to be an unrealistic image of "beauty" because this unrealistic image of "beauty" is marketed very effectively. The list goes on.
What kept religion alive all this time? What kept Christianity thriving? From any angle you look at it, it boils down to marketing. Christianity (along with other religions) are marketed effectively. Possibly the best examples of marketing one can come across.
I look at it this way: with any major or specialty, you can use it for good or you can use it for evil. If one becomes a chemist, he or she can make a living creating new medicines for sick people (good), or they can create new hard drugs for addicts and become drug dealers (evil). The same concept applies with all specialties, including marketing. One can spread good ideas and messages (good), or one can make a living selling and marketing Power Bracelets and other scams (evil).
Science and reason can be promoted (good), and religion and superstition can be promoted as well (evil).
Nearly ever tenet of consumer behavior is exploited for the benefit of religious propagation. Appeals to fear with the threat of Hell, appeals to emotion with the idea that Jesus died for you so you should live for him, behavioral influence, celebrity endorsement.. almost every single one except for the sex appeal. One can imagine, though, how religions would be if they allowed themselves to use the sex appeal in their advertising, marketing, and propagation.
With every new product, there's what's called the "product life cycle." The introductory phase, the growth phase, the maturity phase, and the decline phase. Most products last a few years to a couple decades, while religion has lasted an immense amount of time. Christianity is well past the introductory phase. The parts of it's introduction and beginning story have long come and gone. Over the past couple thousand years, it has spend a lot of its time in the growth phase. More and more people becoming Christian, being loyal to Christianity, and becoming increasingly reluctant to switching brands. Right now, I believe it is safe to say Christianity (and I think religion as a whole) is jumping up and down around the maturity phase. If there weren't new promotions and more market penetration, religion would eventually slip into the decline phase and go out of style. Alas, there are new religious promotions and market penetrations pretty frequently which raises the stocks of religion yet another spike. There new rapture predictions every few years, Noah's Ark is found every few years, religious holidays are sprinkled throughout the year, and every passing year, we are apparently getting ever closer to the "end times." When people start doubting the scriptures, a safeguard comes along and blows the whistle exclaiming that the bible predicted that there would be doubters in the end times, therefore the bible is true... and there is yet another spike.
Of course, there are competing brands of superstitious belief that exist, such as Islam, Judaism, Hindu, etc. and some of those brands are more competitive than others- wanting a higher share of the market. Like cell phone companies, some will engage in deception, misleading claims, and will always claim their brand to be the best.
Some major brands and names in the world have smaller companies under them. Christianity has many denominations under its name. The major brands and bigger brands that have been around longer have a higher customer loyalty base than the new brands that come out. Christianity is a big religion, has been around for quite some time, therefore it has many followers. Occasionally there will be knockoff brands, spoofs, frauds, counterfeits, etc. just like how Scientology, Mormonism, and some of the New Age stuff popped out of virtually nowhere. This of course is definitely not to say that the original brands or religions are the best, more real, or more true- but it just goes to show a stiking parallel.
Religions have simply been the masters of marketing. They utilize almost every human weakness (except sex appeal) and only those who see them for what they really are, are the ones who have the knowledge to break free.
As a Marketing major, I began to see religion as a perfect example of the evils of marketing and the potential it could bring to an entire society of possibly billions of people. If all it takes is marketing to promote such mental atrocities, then marketing can indeed be used for good to promote clear thinking, rationality, and science.