Viral marketing is defined as “any advertising that propagates itself the way viruses do”. E.g. When Hotmail users send emails, they “infect” the recipients with the tagline at the bottom of their messages. Viral marketing denotes any strategy that encourages individuals to pass on a marketing message to others, creating the potential for exponential growth in the message's exposure and influence. Thus, the name “Viral”! Viral marketing is also called V-Marketing, organic marketing, word-of-mouth marketing or word-of-mouse marketing.

Viral marketing works best when it induces websites or visitors to pass on a marketing message to other sites and people, creating a potentially exponential growth in the message's visibility and effect. In simple words, you pass your message on to 10 other people – each of these 10 people pass on that same message to 10 other people and so on. Such collaborative communications, by nature, need others in the chain. Everyone simply tells everyone else. ICQ, a service that prompts you when selected friends or colleagues are also online, is an example of a service that is viral by its nature. Its users want to tell their friends about it so that it will be more useful to them.

Viral communication is clearly an enormous opportunity for creating brand growth. Get it right and the rewards are enormous. Your consumers will spread your message for you, at astonishing speeds to a phenomenal number of people. Get it wrong and your carefully crafted proposition will get little further than the marketing director’s inbox.