Social network theory seeks to understand how individuals are connected to other people and how invisible links between groups can seamlessly connect to amplify trends. The theory is based on a famous 1960s experiment by psychologist Stanley Milgram. A package passed through six pairs of hands before being receivedt; leading to the concept of 'six degrees of separation' between the initial message and the final recipient.
The viral marketer's dilemma is to identify, categorize and target people for initial reception and replication of the vendor's message. The primary message itself should be highly contagious in order for it to be adopted and replicated easily and regularly.
Viral marketing campaigns can be 'low integration', frictionless model where the original consumer is essentially passive in the transaction. The famous example is Hotmail's early 1990s campaign which gave away free e-mail addresses, incorporating a vendor advertisement. Each consumer provided Hotmail with a free distribution network and qualified leads of persons who were already had an email account, and might be interested in switching to free account for their personal correspondence. Campaigns of this type rapidly build customer acquisition and enhance customer retention because the consumer is locked-in to the service as switching will be disruptive.
The alternative is a 'high integration', active marketing campaign where the consumer opts-in to a service or product - newsletters and RSS feeds are obvious examples -- or where the consumer seeks a reward for promoting the vendors goods/services. ...