Viral marketing is a form of advertising where customers voluntarily speak about the product or the advertising measure. Consumers for example tell their neighbors or their colleagues about it. On the Internet the advertising message then spreads like a virus. However, this type of advertising is difficult to control, as the clips have to be well made in order for consumers to talk about them. Most of the clips are one thing above all: entertaining. The product or brand steps to the background.
Often companies camouflage their blogs and video clips so they are not directly identifiable as advertising. If, however, it turns out that it is disguised advertising of the manufacturer, companies often suffer brand damage.
The most popular video on YouTube with the topic of viral marketing (about 2.926.786 hits) http://www.youtube.com/watch?v=YkTDDeuytM8
Example: Viral marketing campaign of a Swabian business (about 743.798 hits)