Peet's Coffee & Tea and Green Mountain Coffee Roasters' fight for Diedrich Coffee was more than just a bidding war. It was acknowledgement of a trend, namely the rise in popularity of the single-cup coffee maker. One in which Green Mountain, with its Keurig machine controlling 58% of the market, already is taking part. But Peet's, which runs a chain of coffee shops, is not. Unit sales of single-cup machines have been growing at an annual rate of 38.7%, compared to just 6.3% for coffee makers overall. And there's plenty of growth still left to be had, as these brewers make up only 10% of total coffee maker sales. What's more, the real money is made in what are called coffee pods, or the individual servings used in single-cup machines. The business plan is to sell the machines relatively cheaply and then profit from consumers' need for refills. Branded Keurig pods are called K-cups.