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. Three-quarters of the respondents said they would buy New Coke again. 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".
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. 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.