I just finished listening to this book {Ponzi's Scheme) by Mitchell Zuckoff. I absolutely love history stories and this book about Charles Ponzi and his use of the "Using Peter to pay Paul" scam is a wonderfully details description of Boston at the turn of the century.
Buried in this story is the story about how to build a viral campaign. In Ponzi's case it ultimately was a scam but there were some very interesting elements. 1) find a customer who would listen and be an advocate, 2) provide a product / service that was interesting, 3) love your customers, 4) provide emotional value, 5) be enthusiastic with the press, 6) believe in your vision and 7) deliver on your promise.
According to Zuckoff's account on Charles Ponzi, Ponzi did just that. He even delivered on the promise for a time until the scheme imploded. According to Zuckoff, Ponzi's downfall was optimism and false hope. But I can see how he truly believed in his product (how misguided it was) and because of this belief virally sold his product to 10's of thousands of customers.