Churn refers to what happens when a user leaves a service, and "service" in this case can describe almost anything from a dialup ISP account to a listserv subscription. Churn is the major concern of almost any e-business, if only because it's so hard to attract users in the first place. Most sites, therefore, have tried to develop "sticky" services to keep us coming back, or encourage us to give them basic pieces of information so they can keep in touch with us.