Trade Collector's Items and More With Online Swap Sites
People wanting to avoid fees might explain the success of some swap sites. But at least in the case of Switchouse, there's more to it. This site cleverly relies on product databases (CDs by Muze, games by IGN, computer stuff by CNet), so that you browse a neat catalogue structure akin to an e-commerce site. Compare that with the mess at Ebay. Switchouse helps people make sure they know what they're purchasing or trading, with a much easier process to go through, from searching/proposing to closing the transaction.

Auctions are relevant for collectors, not commodity items. The swap sites also use pricing models more adapted to instant transactions (as opposed to auctions taking several days to close.)