I have never traded or sold cards, but I have bought several online (mostly on Amazon).  I haven't thought about trading or selling until now, but am drowning in cards and am so analytical that I have spent close to a year working on my one red and green deck. ;-)  So, I'm not sure how this works but I would love to share my entire collection (not that I'm selling all of them) and hopefully find a home for the cards that I don't use and don't believe that I would use. :)