Some people say they are.
I completely disagree.
Not only are business cards an inexpensive way to market yourself and your business at live events, if designed well, they can serve as visual reminders to people when they come across another one of your messages in the digital space, say on Facebook or Twitter.
Business cards also provide something the digital space cannot: the experience of holding and touching something. We learn just as much through what we physically feel as through what we see. The more senses you can touch with potential customers, the better your chances of having them remember you.
A business card does that in a way a website or tweet never could.
When I meet someone new at a professional event, I am not going to hand over my cell phone or tablet for them to see my website or Facebook page.
I am going to give them a business card. Small, neat, tidy.
Something tangible for them to take away.
The day business cards are obsolete is the day no phone rings.