I’ll admit it — I am terrible at remembering birthdays. There’s no excuse, really, considering that practically every major Internet company offers some form of calendar with built-in integration to notify you of your friends’ birthdays. (It’s Facebook’s forte.) E-retailer giant Amazon knows that people like me exist, and wants to make the best of my terrible memory. That’s at least part of the idea behind Amazon Birthday Gift, the company’s Facebook-integrated social gifting product rolling out Tuesday. The concept is simple: Send a friend whose birthday is coming up one of Amazon’s Birthday Gift cards — a virtual gift-card credit to spend on Amazon.com — which won’t show up for your friend until their actual birthday. Other folks (including the forgetful ones like me) come along, and can contribute their own money toward adding to our friend’s birthday gift amount, thus increasing the size of the pot for your buddy’s special day.