Are military personnel vulnerable on social media sites?

you bet!

Unequivocally yes.

Social media has evolved very quickly that it is difficult to keep up with both work and personal/family security in addition to the issues of public image and etiquette. It is now a required (and probably the most effective) media for advertising and public affairs. The invention of SM is as significant as the telephone, radio, TV and even the internet itself. I admit I have gotten bitten by the social media bug for both this site and Facebook; however, in addition to keeping privacy settings high, most importantly, I ask myself, if your post made the front page of the New York Times, would you be comfortable with that and not compromise safety and security of your unit, your family and yourself.

However, the challenges remain. Even when you are cognizant of these things, its getting harder to draw the line of whats safe and whats not. Anything you put out on line can get copied; even if you remove it people can copy and pass it on beforehand. The internet reaches everywhere and the bad guys can piece seemingly harmless information from various places around the internet that can be make it not so harmless. That kind of thing is a real challenge; everyone needs training and education on these kind of things, not just the cyber-warriors.