Explanations on the different ratings
More on the private investigation bit on the MPAA members
This Film Is Not Yet Rated (2006)
The MPAA gave the original cut of the film an NC-17 rating for “some graphic sexual content”: scenes that illustrated the content a film could include to garner an NC-17 rating. Kirby Dick appealed, and descriptions of the ratings deliberations and appeal were included in the documentary. The new version of the film is not rated.
NC-17 is a film rating of the United States film industry used to denote films “No One 17 And Under Admitted” (18 and older ONLY). These films contain excessive graphic violence, sex, aberrational behavior, drug abuse, strong language, or any other elements which, when present, most parents would consider too strong and therefore off-limits for viewing by their children and teens. NC-17 does not necessarily mean obscene or pornographic in the oft-accepted or legal meaning of those words. The Board does not and cannot mark films with those words. These terms are legally ambiguous, and their interpretation varies from case to case.