Here's 3 things you may not have thought to do with your business cards:
1. Tape to bottom of your laptop. If you accidentally leave it somewhere, might be helpful to have all your contact info someplace obvious.
2. Keep folded one in your coat pocket. The adult equivalent of putting your name on the coat tag in marker. If someone accidentally leaves with your jacket/coat, there will be a way to find you. Or a way for you to prove it's yours if someone walks out of wherever you are wearing it.
3. Tape inside your briefcase, carry on, suitcases. Just in case the outer ones are gone (or there is no outer one).