I was just reading up on New Coke and found this on Wikipedia:
Most Coke drinkers resumed buying the new drink at much the same level as they had the old one. Surveys indicated, in fact, that a majority liked the new flavoring.[23] Three-quarters of the respondents said they would buy New Coke again.[22] The big test, however, remained in the Southeast, where Coke was first bottled and tasted...
Despite New Coke's acceptance with a large number of Coca-Cola drinkers, a vocal minority of them resented the change in formula and were not shy about making that known -- just as had happened in the focus groups. Many of these drinkers were Southerners, some of whom considered the drink a fundamental part of regional identity. They viewed the company's decision to change the formula through the prism of the Civil War, as another surrender to the "Yankees".[24]
Company headquarters in Atlanta started receiving letters expressing anger or deep disappointment... The company hotline, 1-800-GET-COKE, received 1,500 calls a day compared to 400 before the change.[14] Coke hired a psychiatrist to listen in on calls and told executives some people sounded as if they were discussing the death of a family member.