It's pretty clear that social media can be a boon to businesses. Which is why some experts and entrepreneurs expect employees to use their own social-media networks for the good of the company. "Get out there and talk about us," is the simplified version of what they want workers to do.

But there's a potentially large downside, as the Olney Charter High School in Philadelphia learned. And even though it's a school, not a typical business, entrepreneurs should pay attention, because the trouble Olney has had could turn up on your doorstep.

A union attempting to organize the teachers at Olney is expected to file an unfair labor practice charge. The group says a new social-media policy is a thinly veiled attempt at reducing the ability of staff to talk.

The new policy reportedly prohibits teachers from "making negative comments about their employer on social media, including in blogs and online forums." It's not hard to understand how a company might want to avoid being slammed by employees. That's a particularly difficult form of bad press.

It's not unusual for companies to take action against an employee who decides to vent, like a waitress fired for allegedly complaining about bad tippers. There was even the University of Mississippi employee who was reprimanded for rooting for a rival football team on Twitter.

The problem a company potentially faces, though, is that some types of communication, even if negative about an employer, are protected under U.S. labor law. Employees are allowed to discuss working conditions with one another. The complication that social media brings into play is that the reach of the conversation can be far broader than a water-cooler discussion. Here are two major observations that the National Labor Relations Board has made about employee use of social media:

  • "Employer policies should not be so sweeping that they prohibit the kinds of activity protected by federal labor law, such as the discussion of wages or working conditions among employees."
  • "An employee's comments on social media are generally not protected if they are mere gripes not made in relation to group activity among employees."

Before deciding to restrict what employees can say on their own time or to fire an employee for something he or she said, talk to a labor lawyer. The nuances of the law are tricky, and being on the wrong side of it can leave you open to a lawsuit and big legal bills.