The real difficulty lies in actually implementing this strategy,many people have failed to simulate the epidemic becuase it is extremely difficult to find those groups of influential people who form the base for the epidemic.There was an article in May '07 issue of Harvard Business Review,Viral marketing for the real world, where in Duncan J. Watts and Jonah Peretti talks about a new variation of viral marketing, the Big seed marketing.

Big seed marketing alleviates the difficulty in simulating the epidemic by using the conventional mass advertising to create a large initial seed(I) for the campaign and here even if the reproduction rate R<1 ,the total number of infections(I/(1-R)) is much better to using just the viral marketing.The authors pointed out that many companies have successfully implemented the big seed campaigns using an open source software called ForwardTrack.