I would think that it would be a good reason for a reprimand. I mean, if you are faking sick & then you post pictures of you doing a keg stand or comments about a party...then yes I think the boss could bring it up. It would have been from the employees carelessness that the boss found it anyway.
Even if you aren't friends with your boss on facebook, whose to say that the employee that you thought was trustworthy wouldn't drop a note their way? I mean, if you are at a St. Patty's day festival, wouldn't they be a little jealous & perhaps want to see your good time have some consequences. Or maybe not...but why take that chance.
Other things to consider, like are you posting mean things about your coworkers/boss, or are you posting pictures of you doing illegal things that someone may not wish to have represent them as a company, or are you being controversial? I think if you are asking this question, you may be looking to stir the pot anyway...if you wouldn't want you boss, your mom or dad or your future mother in law to see it....don't post it! The internet can be abused so easily.....(also not saying this is you asking, just answering in general) :).
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.