It seems that bloggers can’t slag off their bosses whenever they choose.
This CNN article makes it clear that, whilst blogging has appeal to both businesses and individuals, employees are not free to denigrate their employers, even anonymously. They quote examples of employees from Delta Airlines, Friendster, and Microsoft who were fired for posting information online that was deemed inappropriate.
At least in a US setting (it is doubtful the situation would be different in Australia) employees are not shielded by a right of free speech in an employment relationship, and simply because an employee publishes their views online, rather than at work, does not excuse their actions.