1. In 2009, I did a small and unscientific study of user turnover at Epinions, an early Web 2.0 company now part of the eBay empire. See “Frequently Asked Questions about the eBay Announcement,” http://www1.epinions.com/help/faq/show_~faq_announcement (last visited Aug. 27, 2009). My study revealed that two-thirds of Epinions’ top 20 most popular authors in 1999 had turned over in nine years, and 25 percent of Epinions’ top 20 most popular authors in 2003 had turned over in five years. See posting of Eric Goldman to Technology & Marketing Law Blog, “Decay Rates of Committed Online Community Membersan Epinions Case Study,” http://blog.ericgoldman.org/archives/2009/01/decay_rates_of_1.htm (January 26, 2009, 06:09).