Print, TV, Radio, billboards, direct mail and other traditional advertising techniques are push-based. As a result, the consumer is exposed to over 4,000 intrusive marketing messages per day.

Perceived as entertainment worth watching, pull-based viral advertising is fun, non-intrusive and 100% voluntary. Consequently, the consumer willingly engages with the brand and at times even acts as a sales agent by sharing the ads with friends.

Behind it all stands a meme – a catchy idea such as a good joke, rumor or smart saying (Richard Dawkins, The Selfish Gene, 1976). Memes spread by word-of-mouth (WOM) and exhibit the same growth pattern as a self-replicating viral epidemic spreading among a population – hence the name viral. On the Web, this phenomenon is known as viral marketing, eWOM, "consumer-driven" or "word-of-mouse".