Thomas Baekdal identified seven "tricks" to viral or word-of-mouth marketing, where "your campaign will suddenly get a life of its own...Everyone want to see it, and when they do, they all want to share it."
Seth Godin and Malcomb Gladwell and many others have covered this this topic.
Thus this is an old topic in Web time yet his points are straightforward.
Here's the first two:
1: Make people feel something
The most important trick of all is to create a very strong emotion. You need to have an opinion, to express an idea with commitment and dedication. You want people to:
• be filled with love or hate.
• be very happy or insanely angry
• be an idiot or a genius
• be deeply compassionate or an egoistic bitch
You want people's blood to be pumping of excitement. Forget neutral, trying to please everyone, supporting several target groups or any of the many ways to be unbiased. Viral marketing is 100% about emotions.
2: Do something unexpected
Forget about trying to promote your products as just being great - everybody does that. Forget about trying to make it look cool - everyone else has "been there, done that". Remember the bear being attacked by a man? That was unexpected - and it is one the most effective viral advertisements ever.
Methinks the music world continues to blaze the viral trail.
Well, here the medium is the message. It's an attempt to start a viral campaign by offering a free book on (what else) how to jumpstart a viral campaign. Ironically, when you attempt to access the URL it times out.