Starbucks...hit back at critics...[saying] it had sharply increased the average price it paid for its coffee last year... It also said it had doubled…the amount of coffee it bought through the independently verified coffee sourcing and purchasing guidelines known as CAFE... Starbucks has been stung by accusations from...Oxfam and the Ethiopian government...that it was indirectly blocking an attempt by the impoverished African nation to register the trademarks of its key coffee brands in the US…