Yep, there is this thing called OPSEC (operational security).
it is very possible that PVT snuffy, while photographing his buddy SP4 Cleatus standing by his Bradley, could also take a picture someting in the background that could compromise security, and either get people killed or cause missions to fail.
PVT snuffy, in this digital age, can send the images directly from his camera memory stick via email to a third party website, who hosts it in the internet for Abdullah the Al-Qaeda operative to freely browse and plan his next suicide bombing or IED. Sometimes the images can be more blatant than that. These soldiers may see no harm in it, but it can be a big problem. Understandable why they would want to lock this down.
This is the reality. It is a bad enough problem that the Pentagon is considering banning cameras in certain zones of military operation, except where approved and screened. UCMJ does not guarantee free speech for members of the military.
In the old days theys they used to black out lines of text in letters home. Obviously the Military has a ways to go in locking down and filtering email communications and OPSEC as far as digital cameras are concerned. I'm sure we will see many changes in the future.