Public choice theory argues that political actors are self-interested and that this is not necessarily conducive to the public good. When applied to topics such as free trade, public choice is relatively uncontroversial. Few people are shunned from mainstream discourse if they point out that domestic industries lobby for tariffs to shield themselves from foreign competition.
However, if one were to take the same insights and apply them to military contractors or the banking system, it’s very likely that “respectable” people will begin to part company. For presenting evidence that the Federal Reserve is to a large degree the product of banking interests, for example, the great libertarian economist Murray Rothbard was labelled a conspiracy theorist. But why is public choice analysis any less valid in a different context?
http://antiwarlibertarian.wordpress.com/2009/02/07/what-is-a-conspiracy-theory/