The first example of viral marketing is often presented as Hotmail, the e-mail service which saw huge growth when the following clickable link was added to the foot of messages sent by its subscribers:
"Sign up for your FREE Hotmail account."
Hotmail realised this potential, and managed to gain more than 12 million subscribers in 18 months through this particular viral marketing.
It is often, wrongly, perceived that viral marketing means online games. Viral Marketing, however, doesnt only involve online games (those which users play to try to achieve top scores or win prizes and then invite others to participate), It involves anything someone will be inclined to share with others.