The review, bylined Irish Eyes, described a meal at Molten as "the worst dining out experience ever".
Owner Sven Nielsen hit back by reviewing the customers, whom he described as "rather rude", on the restaurant's Facebook page.
Ekim Burger owner Mike Duffy received a complaint from a customer through a private message on Facebook this month.
The owner of the popular burger caravan in Wellington created a storm on social media after he posted a long-winded rant following the complaint.
Tauranga bar and restaurant owners say they are also at the mercy of online forums.
Alan Sciascia, Bay of Plenty and Waikato manager of Hospitality New Zealand, highlighted the problems associated with anonymous reviews.
The issues included difficulty in determining whether the person had actually dined at a particular establishment.
In turn, eateries did not know whether a critical review might be coming from a business competitor.
And that's the problem. There is no transparency.
The fact we don't know whether certain reviewers have a hidden agenda means we should take these comments with, excuse the pun, a grain of salt.