One of my best friends started working for Coca Cola as a part time merchandiser (the guys you see building the in-store displays and stocking shelves) the week they replaced Classic with New Coke. He was cussed at so much for something he knew nothing about by people in the stores as if he were the one that switched it.
That switch in formulas turned out to be one of the most successful marketing blunders ever. Classic Coke sales were higher when they brought it back than before New Coke was introduced.