People who like business cards, use business cards. I think in the future "intentional identity communication" will be moot, where people will either know who you are already, or know how to find you (FB, LinkedIn, Ravelry, etc.). If all you really need is a name and a saved contact, I can see people getting used to not carrying and exchanging stuff. "Back in olden times, your 'wallet' had like a quarter-inch of these business cards, both other peoples' and yours to hand out. Yes, we had back problems."