The "Business Strategy" or "White Knight" Immunity refers to the concept that certain sensitive business information will be protected from discovery in lawsuits. It is the topic of an article in the current issue of Delaware Lawyer magazine by Wilmington lawyers Edward B. Micheletti and Michael A. Barlow.
The article explains that it is not a privilege like attorney/client communications and it is not codified by rule or statute, but several Delaware cases have recognized it as a means to protect delicate company data from litigation abuses that would have inappropriately destructive business consequences, especially in the context of fights for control of a company, but the concept should applies to other types of litigation as well.