Not long ago,complaining about your job or crappy boss happened around the water cooler, at lunch with friends, or at home with your family. But the social media revolution has completely transformed the way we vent about work.

Facebook is practically designed for work complaints. Each user has a network of “friends,” and often many of those friends are work colleagues. But what if your Facebook friend is friends with your boss? That means if you complain about work and your friend comments on it, your boss is going to see your complaint.

“Social media presents a very real opportunity for your messaging and posting to ‘go viral’– spreading well beyond just your groups of friends,” says attorney Martin Sweet of legal website THELAW.TV.

Employers understand this, and for years many have sought to prohibit their employees from posting about work on social networking sites like Facebook and Twitter. But as Steven Greenhouse wrote this week in TheNew York Times, the federal government is getting tough with employers who try to keep a lid on what their employees say online.

Greenhouse writes that the National Labor Relations Board has issued a series of rulings and advisories that have made it illegal for employers to fire anyone who casts the company in an unfavorable light online:

The National Labor Relations Board says workers have a right to discuss work conditions freely and without fear of retribution, whether the discussion takes place at the office or on Facebook.

In addition to ordering the reinstatement of various workers fired for their posts on social networks, the agency has pushed companies nationwide, including giants like General Motors, Target and Costco, to rewrite their social media rules.

The NLRB says that many companies’ social media regulations are simply too broad, and is standing up for “concerted activity,” or the right employees have to act together to improve their working lives.

‘The agency is recognizing that Facebook rants about your work is a lot like commiserating around the water cooler or in the cafeteria, which is typically protected speech,” says Sweet.

Sweet cautions that not all work-related speech is protected, however. For example, your employer can still fire you if you post something negative about a client on Facebook.

There’s a twist to this law though. The protections do not apply to managers and supervisors, because the statute is aimed at employees who are trying to organize to improve their working conditions.

Interestingly, the NLRB regulates only private employers and does not have jurisdiction over federal, state and local governments. Therefore, these new social media regulations do not apply to government agencies – such as the NLRB itself.