There's an old maxim in retail and customer support: "If the customer has a bad experience, they will tell, on average, 13 other people." I've also heard the number as high as 20. Whatever the actual average, it has certainly been increased in the age of near-instantaneous and geographically-unrestricted communications.
I recently saw a blog entry on the del.icio.us/popular list that documented one individual's struggles with HP customer support over a broken video card or motherboard (yet to be determined). Nearly 60 people bookmarked it over the space of a few days. And that's just the people who decided to save the bookmark -- on del.icio.us. Check out the paragraphs under the January 3 heading, where he describes how he sent out emails to a number of large listservs and many people on his address book. He got dugg, and his server was clocked at about 1 hit per second.
HP finally responded. Might have had something to do with Granneman posting the email address of a supervisor at HP, and suggesting people contact HP. Granneman will be receiving a new PC.
What does this tell us? I think it is a perfect example of how one person's experience is shared by many, more so than before email, IM, and social bookmarking. With a compelling story, a reasonably tech-savvy user can influence the buying habits of people who were previously many degrees of separation removed.
So pay attention, industries who depend on customer service and retail: you are talking to the crowd now, not the individual.