i would say that trading cards would -snip- conflict with the basis of the game itself which is to collect not trade.
Magic: the Gathering is designated as a "collectible card game", yet people trade those cards constantly. Trading assists in the effort of collecting. The difference is that M:tG uses physical cards, and no one really cares if you keep several sets in multiple places (similar to having multiple accounts). Here, the cards are just bits and bytes, and having multiple accounts does make a difference. Unless Zanzarino is going to ban all alts and create a way to enforce the ban, there is no way to keep people honest with trading.
I dislike Zanz's decision, but I agree with it.