With no legal precedents to point to, many employers are looking for guidance to a report on social-media firings by the National Labor Relations Board. But cases ruled on by the board illustrate the fine lines involved in determining what online speech is legally protected. To wit:

Protected: Workers who lashed out on Faceboook at a colleague alleged to have questioned their work ethic.

Not protected: A bartender who complained in a post to a relative that he hadn’t had a raise in five years.

Protected: An EMT fired for calling her boss a “scumbag,” in violation of a company policy against bad-mouthing supervisors.

Not protected: A retail worker who complained on Facebook about a manager’s “tyranny.”

Protected: A car salesman who slammed his employer for serving hot dogs at a rollout event for a new BMW.

Not protected: The same car salesman, who also made mocking comments about an accident at one of his boss’s other dealerships. .