What do you know about Viral Marketing?

Viral marketing is a marketing strategy in which advertising or content is not distributed by one company to all target persons (as in classic TV advertising, for example), but the message spreads from user to user, i.e. virally. Companies use viral marketing in the hope of high reach at low cost.

Viral marketing is a sales technique that involves organic or word-of-mouth information about a product or service to spread at an ever-increasing rate. ... Once something does go viral, it is an easy and cheap way for a message to gain popularity.