Michael Shermer in Scientific American:
In 1980 I attended a bicycle industry trade convention whose keynote speaker was Mark Victor Hansen, now well known as the coauthor of the wildly popular Chicken Soup for the Soul book series that includes the Teenage Soul, Prisoner’s Soul and Christian Soul (but no Skeptic’s Soul). I was surprised that Hansen didn’t require a speaker’s fee, until I saw what happened after his talk: people were lined up out the door to purchase his motivational tapes. I was one of them. I listened to those tapes over and over during training rides in preparation for bicycle races.
The “over and over” part is the key to understanding the “why” of what investigative journalist Steve Salerno calls the Self-Help and Actualization Movement (SHAM). In his recent book Sham: How the Self-Help Movement Made America Helpless (Crown Publishing Group, 2005), he explains how the talks and tapes offer a momentary boost of inspiration that fades after a few weeks, turning buyers into repeat customers. While Salerno was a self-help book editor for Rodale Press (whose motto at the time was “to show people how they can use the power of their bodies and minds to make their lives better”), extensive market surveys revealed that “the most likely customer for a book on any given topic was someone who had bought a similar book within the preceding eighteen months.” The irony of “the eighteen-month rule” for this genre, Salerno says, is this: “If what we sold worked, one would expect lives to improve. One would not expect people to need further help from us–at least not in that same problem area, and certainly not time and time again.”
More here.