There are many reasons for the popularity of viral marketing today.
Entire social networks have migrated to the web. A large proportion of everyone's friends and family members are now online or soon will be.
The network effect plays an important role: As more people sign up, they can contact many more, and soon the total number rises exponentially.

Is Viral Marketing All It's Cracked up to Be?
BY Sandeep Krishnamurthy | 5-9-2000 te