They are trying to sell business cards for dating use. It's trying to solve the issue of writing down contact details by simply passing a card to check later online.
This is better than business cards because you don't have to disclose any personal information like email, phone number and address. There's less pressure on both parties as well. I like Cheek'd, it's great for NYC.
(And the marginal case where you want to revoke the ability to view your details after you give out the card, but before the person checks...hmm...)