Grab it and pull it, unless it's essentially flush with the MBP . If flushness is the case I'd get tweezers or something and grab onto something that isn't vital to the card. Of course, I'd look for an eject button on the card, but I bet you already did that.
I'm bummed. Just went to apple store and saw the card but it does not do memory stick duo pro only memory stick ... guess I'll stick with my old usb 12-in-1 reader.