You can love it, you can hate it. But surely you can't stop it. It's the word of mouth, the viral effect that can damage (or even destroy) your brand or can make you a star in a few days. I enjoyed reading a very good article about viral marketing on Le Monde (in French), which usually doesn't cover this kind of issues. Entitled "Les guérilleros du net-marketing" the analysis by Yves Eudes, takes us through a series of cases in which the "clients missionnaires" (sort of evangelist clients) have been able to make the difference, either positive or negative, impacting on a brand image. Blogs are surely playing a role in this sense, creating a new category of "web-lobbying" which can no longer be ignored by brands. The article then goes a step further, investigating the power of online communities and the importance to e-commerce sites of users reviews.