Classifying information as a political tool

Case in point - United States v. Reynolds

United States v. Reynolds, 345 U.S. 1 (1953) is a landmark legal case in 1953 that saw the creation of the State Secrets Privilege, an unofficial but judicially-recognized extension of presidential power.

The widows of 3 crew members of a B-29 Superfortress bomber that had crashed in 1948 sought accident reports on the crash, but were told that to release such details would threaten national security by revealing the bomber's top-secret mission.

In 2000, the accident reports were declassified and released, and were found to contain no secret information. They did, however, contain information about the poor state of condition of the aircraft itself, which would have been very compromising to the Air Force's case. Many commentators have alleged government misuse of secrecy in the landmark case.

http://en.wikipedia.org/wiki/United_States_v._Reynolds