Would be one good way to keep each other up to date.  Making it so the cards from the decks we're using would be packed up and ready to be sent automatically to other players when we start a duel with them.  This way our copies of the game will get their cards and updates for their cards just by connecting to them for duels.  Would help a lot when some players turn up that aren't very talkative on the forums but have cards we don't.

The viruses tho.