Sometimes bad is a perception, sometimes customers didn´t like a flavour or a colour.
Sometimes your target isn´t that target anymore.
Watch out for cultural changes, the economic reality of your consumers.
Take care of them.
Don´t think only in the awesome benefits of your product (not even Apple do that): think about your consumer.
Advertising is not just an AD in social networks, TV, cable, radio, print…it must be a message of understanding between what you have to offer and what can be useful to the people.
Turning BAD to GOOD: cos not even human beings are perfect.