The Employer Will Likely Google You, and Will Likely Seek A Co-Employee "Friend's" complicity (oh, I mean cooperation) to view your postings. The employer will troll for inconsistencies, and for independent reasons to discipline you. Stop posting. Delete offensive or revealing postings about your employment (or job search efforts or employment history)even before seeing an attorney, or commencing a litigation. (It's just good sense, and it avoids problems later should you be fired or harassed). I am contemplating asking that the employer ask its supervisors and managers having contact with my client to produce their social media content that may bear on the issues. After all, the "social media" sword is dangerous at both edges.
Secondly, cases have held that when an employer is placed on notice of a likely litigation, on request, the employer must take steps to ensure that e-data relevant to the issues of the litigation are not erased. Emails and texts can be a "goldmine" of admissions and insights to a manager's real attitude and intent.
There are "privacy issues" associated with seeking discovery of social media postings, but those can be overcome in California by complying with the Code of Civil Procedure requirement that employee's be given detailed notice and opportunity to object that their postings are being sought. The attorneys can help in the process by limiting the scope of their subpoenas to describe the specific postings being sought by date, general content, and author, and by making sure the described content found in the subpoena is highly relevant to the issues.