Dropbox’s referral program is perhaps the most familiar example. Refer your friend to Dropbox, and both you and your friend get extra storage. They could afford to do this, presumably because the additional cost of a little extra storage was minimal compared to advertising costs or other means of customer acquisition. It benefited from network effects, too: the more users there are, the more users will use it together. That entrenches the product and service in popular psyche.
As a store gets larger and more popular, running an informal referral program becomes increasingly impossible, and the cost of painstakingly keeping track of referral figures (who referred who, how much did we reward them) increases. This can distract from a business’s core value proposition. You don’t want to be spending time micromanaging your customer referral program, you want to be spending your time building great products.
The Blair Witch Project marketing campaign used a website designed to convince people that the horror/mystery scenario of the movie was an actual missing persons case. Myrick and Sanchez also visited online message boards to spread rumors about the mystery. The campaign was so successful that many people still believed the movie depicted actual events by the time it was released in theaters.
A study conducted by the Goethe University Frankfurt and the University of Pennsylvania, on referral programs and customer value which followed the customer referral program of a German bank that paid customers 25 euros for bringing in a new customer, was released in July 2010. According to Professor Van den Bulte, this is the First ever study published on the financial evaluation of customer referral programs. The study found that referred customers were both more profitable and loyal than normal customers. Referred customers had a higher contribution margin, a higher retention rate and were more valuable in both the short and long run.
According to a paper by Duncan Watts and colleagues entitled: "Everyone's an influencer", the most common risk in viral marketing is that of the influencer not passing on the message, which can lead to the failure of the viral marketing campaign. A second risk is that the influencer modifies the content of the message. A third risk is that influencers pass on the wrong message. This can result from a misunderstanding or as a deliberate move.