It's a case to case then however, there was one time I posted on Facebook about one act in the university I disliked and after some minutes my boss reacted but I refuted her.True but i think it still depends on the kind of arrangements. There are some companies who take their reputation seriously hence they let their employees know that their social media might be check randomly to ensure that they don't do anything that would spoil the reputation of the company. Especially in a situation where you are working or being used as the face of the company in terms of ambassador and so on. But it becomes wrong when the company does not let the employees know.