Business cards are a pain if you ever want to use the information. Most people don't type them up so if you ever need the information you have to scramble to find the card so you can call/email the person. Once you factor in the time it takes to store the information on a business card Bump is more competitive time wise (but of course I am biased).
At most of the business mixers that I've gone to people later add the contacts to LinkedIn, at which point they can grab a vCard if they need to import it elsewhere. It might be worth looking into the LinkedIn API to see if you can try to get a similar workflow with Bump.
