Starbucks is giving you a reason to become a My Starbucks Rewards member, if the rewards weren't already a reason. The Star Dash lets you earn stars for purchases, which you will be able to redeem for eGift cards.
If you collect 10 stars, you'll get a $5 eGift card and if you collect 20 stars, you'll get a $10 eGift card. Each purchase you make (no matter what you spend) qualifies as one star. If you are purchasing multiple items, it might be more useful to do separate transactions to make the most out of your star earning potential.
You can collect from now until May 28th, so that gives you lots of time to get your Tazo and coffee fixes, plus earn enough stars to get even more Tazo and Starbucks coffee.
(Expiry: 28th May 2013)