Never used real punchcards?? That's impressive... something like ~94% of Americans have them laying around. Whenever I pitch Punchd to a group of people they all have punchcards and they all always forget them at home.
It's just as easy to forget about punch cards on your phone as it is to forget about them in your wallet.
This looks like a great product. I can't wait for you to expand your venues.
Maybe notify a user only for 'popular' punch'd locations?