The spread of a successful but pernicious meme, especially one that parasitises the victims into giving their all to propagate it. Astrology, BASIC, and the other guy's religion are often considered to be examples. This usage is given point by the historical fact that "joiner" ideologies like Naziism or various forms of millennarian Christianity have exhibited plague-like cycles of exponential growth followed by collapses to small reservoir populations.

[Jargon File]