TANSTAAFL's an acronym for the adage "There Ain't No Such Thing As A Free Lunch" originating in the 1940s and later popularized by science fiction writer Robert A. Heinlein in his 1966 novel The Moon Is a Harsh Mistress, which discusses the problems caused by not considering the eventual outcome of an unbalanced economy. This phrase and book are very popular within science fiction fandom, with libertarians, and's often seen being used in economics textbooks. In order to avoid the double negative… (More on Tanstaafl)