"The Information Flow"
Probably the least-obvious victim of routine over-classification of military information is the person best-positioned to actually do something about it—the President of the United States. After all, one of the most powerful informal checks on any president’s powers as commander in chief is the institutional military bureaucracy’s control of the flow of information up the chain of command. Each actor in the system has an incentive to offer a relatively rosy account of whatever it is he’s up to, and the compounding effect of this phenomenon can distort the view of the ultimate decision-makers. This is a problem all large organizations face, but the United States government is the largest organization in the world and especially prone to these kind of issues.
The media is one potential mitigating factor. When something important ends up in The New York Times or on MSNBC a whole different group of people in the administration find out about it, who face a different set of job incentives and may well bring it to the president’s attention. I’ve heard specific, though unverified, stories about solid reporting from Afghanistan making waves inside the Obama White House in terms of policy substance as well as political messaging.
Upon assuming office, presidents tend to adopt monarch-derived metaphysical theories that involve a unitary state apparatus that they themselves personify. Thus incumbent administrations are traditionally friendly to secrecy in a manner that goes beyond their obligation to uphold the law by prosecuting violators of existing statutes. The reality, however, is that real administrations are made up of human decision-makers with limited time and attention and who are better able to do their own jobs in a world where information flows relatively freely.