Can't be beaten
Evolving business model adds new formats and sources to the tried and tested P2P and auction ones. Ever increasing range of goods, new and used, from private individuals to major companies using it as retail channel. Best prices, especially if you can wait for the right opportunity to turn up (it usually does). Improving protection of both buyers and sellers and range of value-adding services to both. Recent competition from Amazon only means both will continue to improve.