With 40+ active sites that buy and sell used gift cards now, the market for buying and selling gift cards is a lot like eCommerce was in the early days of the internet boom. Lots of places to shop with widely varying prices. Since then, shopping comparison sites like PriceGrabber and Nextag have flourished and made online price comparison shopping much easier than going to each site and doing the price comparisons yourself.
What the gift card resale marketplace needs now is a gift card shopping comparison meta-site, a great opportunity for some internet entrepreneurs.
Update: There is actually one such site, giftcardgranny.com, but it isn’t particularly effective and only appears to poll a few sites, which includes Ebay, not a particularly safe place to buy a used gift card.
Giftcardspread.com is also well reputed site for buy and sell gift cards.