Wikipedia

As long as each infected user send in half the mail more than one sensitive user (i.e., the basic reproductive rate is greater than one), the performance standards in epidemiology imply that the number of infected users will grow according to a logistic curve. Adds Wikipedia, that if each user sends mail to more than one sensitive user then in theory the campaign will last forever, or at least until all sensitive users have received the message. Even if the message is not sent as frequently, will continue being sent many more times than it was initially. For example, consider a campaign that begins by sending a message to 100 users. Not all of them forwarded the original message, but some of them may do so. This some can be tested by market research; Let’s say he turns out to be an 80%, and each of these forwarded it to just a friend specifically indicates the Wikipedia Encyclopedia, viral marketing or viral advertising are terms used to refer to marketing techniques that seek to exploit pre-existing social networks to produce exponential increases in knowledge of brand (Brand Awareness) through self-replicating viral processes similar to the spread of a computer virus.

Are typically based on word of mouth through electronic means; use the effect of social network created by Internet and modern mobile telephony services to reach a lot of people quickly. The term viral marketing is also used to describe campaigns of undercover marketing based on the Internet, including the use of blogs, sites apparently amateurs, and other forms of astroturfing designed to create Word of mouth for a new product or service. The goal of viral marketing campaigns is often generate media coverage through unusual stories, by a value much higher than the budget for advertising of the advertising company. He insists to point out, that viral advertising refers to the idea that people will pass and share fun and interesting content.