What types of ethical issues might arise in the use of marketing data?

Ethics surrounding the use of marketing data has become a hot topic in recent years.  The latest trend in marketing is to target individual consumers as much as possible.  One of the methods used to determine how to target those consumers is marketing data.  

The greatest ethical issue surrounding marketing data is privacy.  In recent years, class action lawsuits have been filed over an individual's or a group of individuals data being sold or lost in a public forum.  This data may contain such private information as addresses, phone numbers, birth dates, children, health problems, personal preferences and the like.