Cursing when you stub you toe is one thing. Raging against your coworkers is another. I'll take crying any day. Personally, I don't think it's unacceptable to cry at work. I think showing vulnerability can certainly be disarming and foster trust. I do think it's bad to be out of control of your emotions. If you do cry, it's should be something you allow yourself to do because it's the right time and place.