The popularity of single-serve coffee machines continues to rise. According to market research firm Euromonitor International these devices accounted for 20% of coffeemaker sales in 2011 up from just 4% in 2006. The current leader in this segment with about 75% of the market is the Keurig machine from Green Mountain Coffee Roasters (NASDAQ:GMCR). The device uses Green Mountain’s “K-Cups ” or single-serving coffee pods. When you put the K-Cup in the Keurig it punctures the foil on the top and brews a single cup often in under a minute.   Despite the fact that K-Cups are more expensive ...