Facebook's not just for friends: careless talk costs jobs.
I'm not able to verify this, but it's reportedly from the UK – and there's mention of a P45, the official document received at the end of a period of employment.
Even if it's made up, it contains enough truthiness to be a valuable lesson in the porosity of social media. And the boss (on Facebook late in the evening) gains praise for his swift, humorous and decisive response (though he's acted without recourse to HR and the usual procedure of written warnings).
PR Studies 
This made me laugh too. At UNHCR I was recently explaining that the threat of any employee revealing confidential information (location of offices in Iraq/Pakistan etc) is matched by the threat of criticising employees and the organization on personal accounts.