Production Director Jason Chayes explained that card trading isn’t going to be in this recently announced card based Blizzard game for a good reason, “Obviously there are a lot of games out there that do support trading that are similar within the genre. With Hearthstone, we felt like it was the best experience that instead of having trading, you’ll have a crafting mechanic. So what players can do is take cards that they don’t really need and disenchant those cards to accumulate arcane dust and use that dust to craft new cards."
Plus more on that and a few excerpts from the interview regarding balance in this upcoming card free to play card game. It was just announced at PAX East three days ago.