Facebook has a storied history of firing their employees with no justification based entirely on what they say in private messages in Facebook internal. It's happened to close friends of mine. Companies that adopt the same platform will invariably be allowed to use the same unimpeded and unjust surveillance system. And as has been said in other comments here: this information will be more freely and directly available to the US Government, just as Facebook now builds tools specifically for the government to peruse private personal data.

An individual can opt out of Facebook in their personal lives relatively easily. But it is not an option to reject the primary communication tool of your business -- this platform has the potential of keeping conscientious objectors out of the workforce.