Viral marketing is an intentional or unintentional strategy used to exponentially grow a brand, sales, or product through a phenomenon that encourages people to share a marketing message. There are five points to consider for an effective viral marketing campaign: 1) create value by giving away free products or services, 2) simplify the message to make it easy to replicate and share, 3) involve emotions like humor to engage people, 4) involve people by allowing interaction or engagement, and 5) acknowledge that success is not guaranteed as it depends on many prospects and investment. Examples that demonstrate these points include a doctored photo from the 2002 World Cup and the Zoozoos campaign from Vodafone India.