While you probably won't be able to get Jack Dorsey to buy you a grande spearmint green tea the next time you go for coffee (we should know, we've tried), you can at least use his payment service. Yes, today's the day that Starbucks begins accepting Square Wallet purchases at 7,000 of its stores -- just scan a QR code or NFC-tap your smartphone to make a payment. In 2013, you'll a
