The National Reconnaissance Office (NRO) declassified facts in the Manned Orbiting Laboratory (MOL) in July. As fascinating as the concept of a manned reconnaissance platform is, it was never built, primarily due to cheaper, safer options with unmanned reconnaissance.
What loss to America, then, the MOL? In terms of the MOL as it might first have flow, little or none in terms of national security. Four manned MOLs, in operation for some few years in the 1970s, might well have captured better imagery of hostile nations than did their actual robotic successors, but the US met its surveillance needs without them.
The fundamental loss instead goes beyond even the non-cover story of MOL, and is as much existential as it is operational. As with every seriously considered (which is to say, financially supported) space station proposal in the history of astronautics, MOL was not merely a spacecraft. Instead, the spacecraft that was MOL was the beginning of a system. Little was done to study what MOL, if continued, could have become, but what it could have been remains to this day as far on the horizon as it was in 1969.