From the update:
We've built in a great little incentive system which combines fun, momentum, and extra goodies for our backers. It takes the form of SHARES and BACKERS. If we hit x-amount of shares we'll add cards into the core box. If we hit y-amount of backers we'll add even more cards. Every box gets these extra cards completely free and we really want to give you as many cards as possible!
SHARES are free. They cost no one absolutely any thing. Get your friends and their friends to go to our homepage and hit the SHARE option at the top and they contribute towards the extra content. It's as easy as that.