Yes; specific military plans. Study the details of the Normandy invasion for one of the clearest examples in history. Specific capabilities of military hardware is another example.
Mind you, I don't disagree that some unsavory things get hidden behind that curtain. I wouldn't even disagree that the majority of things hidden behind that curtain in modern times may be unsavory. Unfortuantely, the solution isn't as simple as just removing the curtain.
I read Derpderpderp's comment to be referring to the existence of plans, not the specifics. The existence of the Normandy invasion plan was hardly a secret. It was unavoidable that the Germans would be able to tell a major offensive was being prepared. And one very clear candidate was for the Allies to take the more direct route and hop across the channel. The exact specifics (where paratroopers were being deployed and when, which beeches were to be hit etc) are important secrets and my reading of his comment is that they should remain secrets. But the actual existence of the plan was obvious and should not be secret.
The militarily valuable secret is that the Normandy plan was that that was the one the Allies were counting on. There were other plans, for example the plans for the invasion of Sicily surreptitiously delivered into German hands by Operation Mincemeat. Or plan to attack from Norway using Edinburgh as a staging post as part of Operation Fortitude was another candidate. But the existence of the plan is the
You do lose some military information. If the enemy knows you have the capability to track someones movements based on his phone number, they are likely to take mitigating measures. But without revealing this capability, its impossible to have a democratic debate on the appropriate safeguards necessary.
Most street level drug dealers were operating under the assumption that the government could track cellphones. Osama bin Laden apparently went to great lengths to avoid being associated with phones used in communicating details.
I would call cellphone tracking an open-secret: everyone that would benefit from the knowledge already had guessed it, but the government was denying it to the citizens for their own benefit.
The system I have in mind will require all information to be open unless the order to be kept secret unless signed by a randomly selected federal judge. The government should make the case to keep stuff under the lid.
After all the judges go trough a lot of vetting and rigorous confirmation process so probably they do have enough clearance to be kept in the loop.
But the person that keeps the information secret should not the one that makes the rules what is secret.
Mind you, I don't disagree that some unsavory things get hidden behind that curtain. I wouldn't even disagree that the majority of things hidden behind that curtain in modern times may be unsavory. Unfortuantely, the solution isn't as simple as just removing the curtain.