Ten percent of Starbucks transactions in US come via mobile payments

Mobile payments has proven to be a very difficult nut to crack. Google, Isis, and others have failed to bring wallet-free payments to primetime, but one company has seen some success: Starbucks. The coffee chain says that wholly ten percent of its payments in the US are made using smartphones, according to The Wall Street Journal. That's about four million transactions per week. The company has long been the champion when it comes to mobile payments, thanks to its simple apps for iOS and Android...