In what I would consider to be a natural evolution of the medium, marketers are spamming Napster users with instant messages based on the songs that they’re sharing. If there’s anything that might kill Napster (and Napster clones), this is it. If the cost of sharing music through Napster is not only some of your bandwidth, but also being involuntarily subjected to marketing campaigns, then the number of people who opt to share their MP3s might drop precipitously, thus exacerbating the free rider problem.