Basically, its a question of maintaining operational security, or opsec in DoD speak. Anything that even hints of a location, the results of an operation past or certainly planned operations, numbers of people, capabilities, armaments, etc, etc. Anything that would give the enemy any info about your location, disposition, intentions, capabilities or morale.
You may or may not remember when Geraldo Rivera had his creds lifted and was summarily booted out of a 101st base camp and out of Iraq during the initial push to Baghdad for drawing, on live TV, a map in the sand and showing troop locations relative to Iraqi troop locations? That kind of thing is a definite no-no!
After a suitable period of chastisement, retraining and mea culpas, he was let back in, but not into the 101st AO.