If they follow the model of all other MMO's cartel coins will be like SOE station points. Cash for points that buy items or other game stuff. They will be non tradeable and the items will be bound to the character only(EQ or EQ2 or DDO) or available to all characters on that account (dcOnline) when bought. This is why the coins will be bound to the account and not per character.
I highly doubt the items will be tradeable and will not pose as a game breaking items also.
If people expect to trade these dont get in a uproar if they are not or expect them to be.
Other games with boxes are the exception in the way that the keys can be traded or sold on their AH. Even items opened with the keys can be (since that would not hurt people getting duplicates and not be able to use them).
But items bought straight like a vanity item or xp boost or whatever not attached to the boxes are bound on pickup like you said.