A while back I wrote a piece titled Pros and Cons Of Digital Business Cards. In it I listed a few of the benefits for digital business cards (e.g. creating an edge when meeting new clients) and reasons against.
But one thing I forgot to consider was the ratio of sharing. For a digital business card, the ratio is usually 1-1, and I imagine it would be quite rare for that person to forward it on. Yet with one physical card, it can sit on a bench and be seen by multiple people passing by. The ratio could be anywhere from 1-2 to 1-Unlimited depending on where it's placed. It's like a mini-billboard until it's collected, often promoting your name/business to more people in one go.
The great thing about this for my freelancing is that I can promote my UX/UI and design work with physical business cards (see below), while promoting my startup (http://barkles.com) in person/digitally. Even though I look forward to the day when we don't 'need' to use physical business cards, it's worth making the most of both avenues now.