Or, you can put a QR Code on a business card that represents a valid vCard, such as what I have done:

http://i.imgur.com/HpbLO.png

This allows someone to grab their mobile phone, scan the QR code and save the information to their address book. Now if they lose the card they still have my information on their smartphone.

I handed out many such cards at Black Hat and DefCon and they were a huge success with people.