Viral Marketing (vi-ral mar-ket-ing)

can refer to on-line or off-line marketing. Any pass-along or non-oral marketing activity that stimulates person-to-person communication about a product, service, experience or entity. A marketing phenomenon that facilitates and encourages people to pass along a marketing message. Viral marketing depends on a high pass-along rate from person to person. If a large percentage of recipients forward something to a large number of friends, the overall growth snowballs very quickly. If the pass-along numbers get too low, the overall growth quickly fizzles. At the height of B2C it seemed as if every startup had a viral component to its strategy, or at least claimed to have one. However, relatively few marketing viruses achieve success on a scale similar to Hotmail, widely cited as the first example of viral marketing

When consumers experience non traditional campaigns, they tell others, this is an example of viral marketing.