yes something called personal security, your image, status and formation can be used to gain intelligence, you dont even have to be anybody special, intelligence agencies look at the bottom of the pecking order so to work out Orbat and Movements.
Also anything you do online that can bring the army in disrepute will be used against you by the media.
Also you are also open to influence criminal, terrorism and foreign. You let it slip that you are the crypto custodian, you may find yourself being pressured into handing over a sheet or two of it.
We have even investigated a chap who was really pig ugly managing to pull a gorgeous chinese lass that premier league ahead of him. This led to a major security breach.
If you want to put up war porn, it up to you, but after seeing soldiers lives and careers ripped apart because of facebook for the smallest of reasons I would say no. I have a facebook account and there are zero pictures of me in uniform nor do I allude to being in the army. Anyone asks I am a underwater wood welder for a lumberjack firm.
Play it safe, its all fun and if you get chatted up by a random chinese lass then it confirms you are pig ugly, looking a John Lennnon.