Word of Mouth vs. Incentivized Viral Marketing

Mark Joyner makes a powerful distinction between inspired Word of Mouth marketing and incentivized Word of Mouth marketing. He says that the viral marketing tools don't really work as evidenced by the their lack of continued viral traffic, which can be verified on Alexa. He said what you'll see is an initial surge, because of product launch and then a huge drop. I tested his argument and found it to be true on Mike Filsaime's Viral Friend Generator. Here's Viral Friend Generator's embarrassing Alexa graph.