Starbucks’ rewards cards are a tool for more than just loyalty:

Starbucks has around $1.6 billion in stored value card liabilities outstanding. This represents the sum of all physical gift cards held in customer’s wallets as well as the digital value of electronic balances held in the Starbucks Mobile App.

Now even though this is money that Starbucks owes its customers and is therefore a liability on its balance sheet,

Starbucks… doesn’t have to keep customer funds in a low yielding segregated account or government bonds. Why is that? PayPal allows people to cash-out of PayPal dollars into regular dollars, so for regulatory purposes it must keep an adequate reserve on hand to facilitate redemptions. But the only way to cash out of Starbucks balances is to buy a coffee–a promise that Starbucks can always keep! And so Starbucks can immediately put its customer loans to work in higher-yielding opportunities like funding its operations and expansion.