Be careful when deciding which colleagues to add as a Facebook friend as one throwaway status update about your employer could see you facing the sack.

Our recent story about companies sacking employees over seemingly private Facebook chatter has provoked several new examples from readers who claim their employers took their Facebook postings out of context and used them as an excuse to show them the door.

In almost all cases a colleague had seen the Facebook posts and passed them on to the boss.

Steven Penning, a partner with Turner Freeman with two decades of experience in workplace law, has said people who are sacked over social network comments could have grounds to file an unfair dismissal claim, as employment contracts rarely cover staff use of social networking sites.

"What employers are doing is they're scrambling and trying to make out that present policies can be stretched to cover these new areas, and in many respects they can't," Penning said.

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MashUp Blog: Have you been threatened over social network comments?
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 About three weeks ago, Roseanna Brisbane, after a long day doing casual work for a Queensland Government agency, updated her Facebook status saying that in future she would be "saying no to working for shitty Government departments".

She did not name the department or any individuals in her message but a colleague and Facebook friend saw the update and passed it on to her boss. She was promptly "escorted out of the building" on her next day back at work.

She said she was a casual so had few options in terms of unfair dismissal claims.

Brisbane, 20, believed she was targeted because of a back injury she obtained at work that restricted her productivity.

Her mother, Jillian, said she could understand critics who say people should be careful about what they publish online. But young people saw Facebook as their main tool for communicating privately with friends and did not expect their bosses to be spying on them.

"It is becoming the Soviet state type thing where you're scared of talking to someone in case they go and tell someone else," she said.

Similarly, a reader, Faith, wrote in to say she was dismissed because she complained in a Facebook status update that the company she worked for was discriminating against her because she had a mental illness. Again, Faith was dobbed in by a co-worker whom she accepted as a friend on Facebook.

"The company used this as an excuse to sack me because I had been ill for so long," she wrote.

Jane Morgan was fired from her job at a small construction management company in the Sydney CBD in January after she wrote a message on a friend's Facebook wall saying the company "sucks".

The friend had just lost his job with the company and Morgan said she was "just trying to make him feel better".

"The way I do that - my generation - is sarcasm and joking around in jest," she said.

However, Morgan said one of her managers saw the Facebook comment and forwarded it to a company director, who forced her to resign.

Morgan was shocked as she believed her work with the company had been excellent, and in fact she received a bonus the week before she was sacked. The company was sponsoring her to stay in Australia and now Morgan is struggling to find a permanent job, and may not be able to stay.

Morgan admitted her Facebook comment was not appropriate but she only ever intended it to be directed at one person.

"It was taken out of context - if you look at it in context I was actually very happy working with the company," she said.

Morgan said she investigated filing an unfair dismissal claim but workplace laws introduced by the Howard government prevented her from doing this as claims could only be made against firms with more than 100 employees.

Changes by the Rudd Government, which come into effect on July 1, mean only firms with fewer than 15 employees are exempt from unfair dismissal claims.

A reader, Jenny, said she was given a final warning and threatened with legal action after she updated her Facebook status to say she was "over work". She had been working at the company for eight years.

Another reader, Bummer, was fired from his job on his first day over Facebook comments he made regarding the company's long recruitment process. He did not mention the company name and expected the comments were private but later found out he was not using the correct Facebook privacy settings.

"I don't agree that employers should use social networking tools to learn more about their employees as most people's 'social' personality and 'work' personality are vastly different. I definitely learned the hard way," the reader said.

Last week this website reported several other examples of Australians being sacked or disciplined over seemingly innocuous online posts, including the case of a man who says he was fired from his job at a "large corporate bank" for using the word "recession" in his Facebook profile.

Furthermore, the NSW Department of Corrective Services is threatening to sack prison officers over posts they made to a Facebook group criticising the cash-strapped State Government's plans to privatise Parklea and Cessnock prisons.