Seth Godin seems to inspire people when it comes to word of mouth and viral marketing. He inspired Jennifer Laycock to write an interesting article about how viral marketing is not the same with word of mouth. Read her article here.

Also, Lorna Li has mentioned his and other views regarding Buzz Buzz marketing, word of mouth marketing, guerrilla marketing and viral marketing. Article here.

Seth Godin`s article about the same issue here.

Update: yet another article approaching this subject written by Robert Gorell, here.