Viral marketing and viral advertising refer to marketing techniques that use pre-existing social networks to produce increases in brand awareness or to achieve other marketing objectives (such as product sales) through self-replicating viral processes, analogous to the spread of pathological and computer viruses. It can be word-of-mouth delivered or enhanced by the network effects of the Internet. Viral marketing is a marketing phenomenon that facilitates and encourages people to pass along a marketing message voluntarily. Viral promotions may take the form of video clips, interactive Flash games, advergames, ebooks, brandable software, images, or even text messages. The basic form of viral marketing is not infinitely sustainable.

It is claimed that a customer tells an average of three people about a product or service they like, and eleven people about a product or service which they did not like. Viral marketing is based on this natural human behavior.

The goal of marketers interested in creating successful viral marketing programs is to identify individuals with high Social Networking Potential (SNP) and create Viral Messages that appeal to this segment of the population and have a high probability of being passed along.

The term "viral marketing" is also sometimes used pejoratively to refer to stealth marketing campaigns—the use of varied kinds of astroturfing both online and offline to create the impression of spontaneous word of mouth enthusiasm.

• See Viral phenomenon

History

The term Viral Marketing was coined by a Harvard Business School professor, Jeffrey Rayport, in December 1996 article for Fast Company The Virus of Marketing. The term was further popularized by Tim Draper and Steve Jurvetson of the venture capital firm Draper Fisher Jurvetson in 1997 to describe Hotmail's e-mail practice of appending advertising for itself in outgoing mail from their users.

Among the first to write about viral marketing on the Internet was media critic Douglas Rushkoff in his 1994 book Media Virus. The assumption is that if such an advertisement reaches a "susceptible" user, that user will become "infected" (i.e., sign up for an account) and can then go on to infect other susceptible users. As long as each infected user sends mail to more than one susceptible user on average (i.e., the basic reproductive rate is greater than one), standard in epidemiology imply that the number of infected users will grow according to a logistic curve, whose initial segment appears exponential.

Among the first to write about algorithms designed to identify people with high Social Networking Potential is Bob Gerstley in Advertising Research is Changing. Gerstley uses SNP algorithms in quantitative marketing research to help marketers maximize the effectiveness of viral marketing campaigns. It is also named "viral" because it allows a message to spread like a virus. In 2004 the concept of Alpha User was released to indicate that it had become now possible to technically isolate the focal point members of any viral campaign, the "hubs" who are most influential. Alpha Users can today be isolated and identified, and even targeted for viral advertising purposes most accurately in mobile phone networks, as mobile phones are so personal.