With the many methods available for anyone to get a business card, there is just no excuse not to have one. A business card is a useful tool for everyone regardless of their specific employment status.
Certainly if the company that you work for provides a card, you'll want to carry that. But even if they do, you might want to carry a second card to promote another area of your interests or expertise. For example, if you are working, but actively looking, or have a second job or area of interest, perhaps having a second card to distribute at networking events would come in handy.
Certainly if you are not working, a business card is a necessity. You'll want to create something clean, crisp and easy to read; Something that clearly identifies who you are, how to connect with you and a truncated version of what you can bring to the table.
Once you have the appropriate card(s), carry them EVERYWHERE! Whether you go to the grocery store, on vacation, to your child's sporting events, the theatre, out to dinner...wherever you go, make sure you have a couple of cards with you. You never know when opportunity will strike! Be prepared