Appeal to fear

An appeal to fear (also called argumentum ad metum or argumentum in terrorem) is a fallacy in which a person attempts to create support for his or her idea by increasing fear and prejudice toward a competitor. The appeal to fear is extremely common in marketing and politics.

Logic
This fallacy has the following argument form:
 * Either P or Q is true.
 * Q is frightening.
 * Therefore, P is true.

The argument is invalid. The appeal to emotion is used in exploiting existing fears to create support for the speaker's proposal, namely P. Also, often the false dilemma fallacy is involved, suggesting Q is the proposed idea's sole alternative.

Fear, uncertainty and doubt
Fear, uncertainty, and doubt (or FUD) is the appeal to fear in sales or marketing; in which a company disseminates negative (and vague) information on a competitor's product. The term originated to describe misinformation tactics in the computer hardware industry and has since been used more broadly. FUD is "implicit coercion" by "any kind of disinformation used as a competitive weapon." FUD creates a situation in which buyers are encouraged to purchase by brand, regardless of the relative technical merits. Opponents of certain large computer corporations state that the spreading of fear, uncertainty, and doubt is an unethical marketing technique that these corporations consciously employ.

Image wars
Although FUD was originally attributed to IBM, the 1990s saw the term become often associated with industry giant Microsoft. The Halloween documents (leaked internal Microsoft documents whose authenticity was verified by the company) use the term FUD explicitly to describe a potential tactic against Open source software. More recently, Microsoft has issued statements about the "viral nature" of the GNU General Public License (GPL), which Open Source proponents purport to be FUD.

As persuasion
Fear appeals are often used in marketing and social policy, as a method of persuasion. Fear is an effective attitude changer, especially fears of social exclusion, and getting laid-off from one's job. Fear appeals are nonmonotonic, meaning that the level of persuasion does not increase in proportion to the amount of fear that is used. A study of public service messages on AIDS found that if the messages were too aggressive or fearful, they were rejected by the subject; a moderate amount of fear is the most effective attitude changer. Noam Chomsky, among others, has suggested that the appeal to fear plays a role in social oppression on a large scale. According to this belief, political institutions and the mass media use the appeal to fear to foster conformity and maintain the status quo.