What does "doomsday cult" mean? I had been under the impression that it referred to groups like Heaven's Gate or Family Radio which prophesied a specific end-times scenario, down to the date and time of doomsday.

However, Wikipedia suggests the term originated with John Lofland's research on the Unification Church (the Moonies):

Doomsday cult is an expression used to describe groups who believe in Apocalypticism and Millenarianism, and can refer both to groups that prophesy catastrophe and destruction, and to those that attempt to bring it about. The expression was first used by sociologist John Lofland in his 1966 study of a group of Unification Church members in California, Doomsday Cult: A Study of Conversion, Proselytization, and Maintenance of Faith. A classic study of a group with cataclysmic predictions had previously been performed by Leon Festinger and other researchers, and was published in his book When Prophecy Fails: A Social and Psychological Study of a Modern Group that Predicted the Destruction of the World.

(This is the same When Prophecy Fails that Eliezer cites in Evaporative Cooling of Group Beliefs, by the way. Read the Sequences, folks. Lotsa good stuff in there.)

Wikipedia continues, describing some of the different meanings that "doomsday cult" has held:

Some authors have used "doomsday cult" solely to characterize groups that have used acts of violence to harm their members and/or others, such as the salmonella poisoning of salad bars by members of the Bhagwan Shree Rajneesh group, and the mass murder/suicide of members of the Movement for the Restoration of the Ten Commandments of God group. Others have used the term to refer to groups which have made and later revised apocalyptic prophesies or predictions, such as the Church Universal and Triumphant led by Elizabeth Clare Prophet, and the initial group studied by Festinger, et al. Still others have used the term to refer to groups that have prophesied impending doom and cataclysmic events, and also carried out violent acts, such as the Aum Shinrikyo sarin gas attack on the Tokyo subway and the mass murder/suicide of members of Jim Jones' Peoples Temple group after similar types of predictions.

So, "doomsday cult" seems to have a lot to do with repeated prophecies of doom, even in the face of past prophecies being overtaken by events. So far as I know, SIAI seems more to err on the side of not making specific predictions, and thus risking running afoul of getting evicted for not paying rent in anticipated experiences, than in giving us a stream of doomish prophecies and telling us to forget about the older ones when they fail to come true.

Reading on:

While a student at the University of California, Berkeley Lofland lived with Unification Church missionary Young Oon Kim and a small group of American church members and studied their activities in trying to promote their beliefs and win new members for their church. Lofland noted that most of their efforts were ineffective and that most of the people who joined did so because of personal relationships with other members, often family relationships. Though Lofland had made his sociological interests clear to Kim from the outset, when she determined that he was not going to convert to their religion he was asked to move out of their residence. [...] Lofland laid out seven conditions for a doomsday cult, including: acutely felt tension, religious problem-solving perspective, religious seekership, experiencing a turning point, development of cult affective bonds, and neutralization of extracult attachments. He also suggests that individuals who join doomsday cults suffer from a form of deprivation.

I haven't been able to get a hold of a greppable copy of Lofland's book. I'd be interested to see how he expands on these seven conditions. Some of them very well may apply, in some form, to our aspiring rationalists ... I wonder to what extent though they apply to aspirants to any group at some ideological variance from mainstream society, though.