*yawn*
This is nothing new or even that interesting.

At the level of an idea it is certainly novel and satisfying.
However, this idea cannot be carried in your wallet.

It’s brilliant when the “used” items that are stamped can be handled and stuck in a wallet, but not so much when the disgusting items are (eg. yogurt tops, etc.) Still, I absolutely love the idea.

Nice idea. Doesn’t have to be on scraps of paper. Could around stamping it on walls, posters, anywhere.

Carrying it is less elegant than carrying cards, but don’t most people have some kind of backpack / laptop case / hip urban carryall these days?

Great Idea! I think that I must try this one out

It’s nice to see people trying to care for the environment, however if you’re in a corporate business i don’t think that kind of business card will be appropriate. Although small businesses might just be able to get away with business cards like that.