As I understand it, every Starbucks customer that arrives with a reusable cup marks off a cross on a black chalkboard. The 10th person to arrive with a reusable cup gets his or her coffee for free.
This initiative is the result of a competition started in April. Apparently, ‘Starbucks was sponsoring the contest as part of its aim to serve 100 percent of its hand-crafted beverages in reusable or recyclable cups by 2015.’
Here is a link to a summary poster of the scheme.
Sounds fun. The winning initiative was only announced yesterday so I hope someone reports seeing this in action soon!