(CNN)-- RIP, Tab. After nearly 60 years, Coca-Cola is discontinuing its first-ever diet soda, Tab, which acquired a huge fan base in the '70s and '80s and maintained a small but devoted following through the years. "Tab had an amazing run," said Robert Bixby, executive director of the Concord Coalition and a longtime Tab enthusiast. Bixby said messages of condolences have been pouring in. "As a business decision I can understand it, but it's a very sad day ... I do feel it's like losing a friend." Tab is one of several "underperforming" products Coke has said it is eliminating...