The Metrocard has been letting New Yorker slide in and out of subway stations for close to 16 years.
Pretty much as long as I've been a resident of this great city.

When it first debuted, I remember lots of advertisers and local tourist stops using the backs of the cards for messages and promotions. But, others have used this little 3x2 card as a canvas for paintings and silk screens. Or, used discarded cards to make origami-like objects.

It's better than chucking them on the ground (which most people do.)

Here, take a look.