Deena Pawson posted comments saying "work sux" and working until midnight was "gay like the management".
But when Ms Pawson's boss read the comments she was fired for serious misconduct, claiming the online comments had brought The Warehouse into disrepute.
News of her sacking comes after another case of electronic communication going wrong, which led to a viral email sweeping the country with details of a row between a catering company manager and a customer.
Margaret McHugh of the Gourmet Food Store in Auckland told an accounts and event manager at Ray White in Auckland, "I expect you still believe in Santa Clause".
Following the latest case, Ms Pawson of Whangarei said she was just having a bad day at work and does not think the comments justify her sacking.
Employment lawyer Ashley Sharp said employees are free to make comments about their workplaces as long as they do not seriously harm their employer's reputation.
He said employees' freedom of expression in the Bill of Rights has been recognised in past rulings. However, like defamation and libel law, it is limited.
Mr Sharp said he would be surprised if there was not some history to Ms Pawson's case that has not been revealed.
He said Ms Pawson's comment - that working until midnight was "gay like the management" - has to be seen in a 2007 context.
"What does that mean? Gay is a word that is used in different contexts. It certainly has no sexual connotations. I've heard it used in different ways, even to the point where it is used instead of crappy.
"What's wrong with saying that? I think it's fair to say shift work is crappy. Who likes working shift work when other people are at home and you could be with your family," Mr Sharp said.
He said it's a different matter if an employee uses a website to carry out a vendetta against an employer.
The Warehouse did not respond to a request for comment.
