A small Spanish start-up named Fon is becoming a big issue for Starbucks. And Fon doesn't even sell coffee. In late February, the wireless-community builder launched a marketing campaign called "Fonbucks," giving away Wi-Fi routers to Starbucks' neighbors around the country. The idea was to get Fon routers close to Starbucks customers trying to connect to a wireless network, giving them a choice between $2-a-day Fon Wi-Fi access or $10 Starbucks T-Mobile access.