These people are able to get free refills during their visit on hot brewed or iced coffee, or hot or iced tea. Starbucks revealed to Axios that over the past three weeks, “the number of ...

Gupta, Sunil, Carl F. Mela, and Jose M. Vidal-Sanz. "The Value of a 'Free' Customer." Harvard Business School Working Paper, No. 07-035, December 2006.