I do like the concept, and I also agree with the sentiments of others about how a physical biz card is an important tool.

I would suggest to make this better would be to make it a hell of a lot faster to receive cards;

Allow all the functionality you currently have (i.e. write something on the contact, add to contacts etc) -- but also allow you to push cards into a To-Be-Sorted bucket of a recipient.

THis would allow people to push their cards into the bucket of another in 15 seconds and walk away.

You dont want to bog down interactions with people for long as they are trying to share the card/contact and move on with their convo or move to other people.

I would also recommend the ability to have an event bucket/tag that anyone can see and let anyone push their card into that bucket.

For example - I go to a mixer "Cool things" and when I get there (gps recognizes I have arrived) my card shows up in the "cool things" mixer directory of people who have arrived/are there.

Then later - I can go back and look through the bucket and select the people I interacted with and grab their cards. I can do this after the fact when I have time and it wont interfere with the flow of any conversations.