Companies can't possibly approve all social media comments and photos their employees post; those could amount to millions per day for the largest enterprises. And I would hope that companies would realize what a bad policy that would be.
What they need to do is to implement strict rules and guidelines about what can't be disclosed, and then they must raise awareness among their employees about the dangers that lurk in social media. If they have confidentiality rules already in place, they need to make sure that they explicitly mention social media. In other words, employees must become informed self-censors, always careful not to make inappropriate public posts that could be discovered by management.
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