In addition, the U.S. National Labor Relations Board, , ruled against employers who fired workers for complaining on social media sites about work conditions. The agency's position is that discussing work conditions with other employees is protected by the National Labor Relations Act.

Employees should be careful about "inappropriate" work-related posts on Facebook and other social media sites, said Paul Stephens, director of policy and advocacy at the Privacy Rights Clearinghouse.

"There's no doubt that the growth of social networking has created a paradigm shift for organizational security monitoring," he said in an email. "Employees should be aware that their activities may be monitored by their employers, although the precise legal parameters for doing so will need to be developed."

Employees should make use of privacy controls on most social networking sites, Stephens said.

John Simpson, Consumer Watchdog's Privacy Project director, criticized "corporate spying" in the name of security.