1. The fee on real estate and vehicles was fixed because of government regulations. eBay also collected a small fee for posting a secret reserve price and for various listing options. It also received revenue from advertising and partnering.
2. The auction thus has the feature of a Vickery auction with the winner paying the valuation of the second-highest bidder.
3. See Kollock, p. 117.
4. See Avery, Resnick, and Zeckhauser (1999) for a theory of online evaluations similar to a reputation system.