In a recent Legal Interpretation, the FAA Office of the Chief Counsel responded to a request for a definition of what it means to be "in furtherance of a business" in the context of the limitation upon sport pilot privileges. As you may know, FAR § 61.315(c)(3) prohibits an individual exercising sport pilot privileges from acting as pilot in command of a light-sport aircraft when he or she is (1) carrying a passenger or property for compensation or hire, (2) operating for compensation or hire, or (3) operating in the furtherance of business.
The Interpretation notes that, rather than actually defining "sport and recreational flying", the intended limitation on sport pilot operations, it made more sense to define the types of operations that were not permitted for a sport pilot. This was "intended to better clarify [the FAA's] original intent and align the privileges and limitations of a sport pilot certificate with those of a recreational pilot certificate found in FAR §§ 61.101(e)(3) through (5) (prohibiting a recreational pilot from acting as pilot in command of an aircraft "in furtherance of a business.")
The FAA also wanted to distinguish the sport and recreational pilot privileges and limitations from those of private pilots under FAR § 61.113(b) (permitting a private pilot to act as pilot in command of an aircraft for compensation or hire in connection with any business or employment if the flight is only incidental to that business or employment and the aircraft does not carry passengers or property for compensation or hire.) The Interpretation observes that "[f]lights typically permitted to be carried out by a private pilot under the provisions of § 61.113(b) would not be permitted to be engaged in by a person exercising sport pilot privileges."
To further explain this limitation, the Interpretation notes that "flights in which transportation is provided for a business purpose, 'even if incidental to your employment or the business you intend to conduct, and not required by your business or employment would be considered in furtherance of a business.'" Thus, if a flight is conducted for a business purpose, even if it is only incidental to that purpose, then the flight would be considered to be "in furtherance of a business" and could not be conducted by a sport pilot.
Finally, it is important to note that "the restriction on the use of a light-sport aircraft in furtherance of a business is not based on the certification of the aircraft being used but rather on the certification of the airman operating the aircraft." As a result, light-sport aircraft may be used in furtherance of a business etc. provided the flights are operated by an airman with a private pilot or higher certificate.