It was probably inevitable. As online discussion forums have grown in popularity, so too have some highly questionable marketing tactics aimed at harnessing the power of free and influential “viral” communication. Whether it is a plug for your own enterprise or a swipe at a rival's business, the practice has been relatively unchallenged. But new laws coming into effect shortly could see expensive defamation cases result from these supposedly anonymous postings.

Faking a review seems mostly harmless and increasingly consumers are cottoning on to the fact that anonymous does not necessarily mean disinterested. Few, for example, were entirely surprised when the chef in an episode of Ramsay's Kitchen Nightmares admitted that glowing reviews of his restaurant were not in fact written by real customers.

But legal peril is everywhere. We have already seen expensive proceedings result from internet gossip. The most serious recent example came last year when Coca Cola launched legal action in Argentina against rival Danone and its marketing agency Euro RSCG. The case hinges on a claim that Danone – purveyors of Evian – spread rumours on the internet that Coca Cola's Dasani water was 'cancer water' and came from a tap.

If such a case were to come to court in the UK, the most likely scenario is that the owner of the brand subject to the “smear campaign” would issue the perpetrators with a libel claim with all its associated costs and damages. In some circumstances, companies could be sued for the actions of their employees, even if they knew nothing about them.

And there's often nowhere to hide – even the internet's apparent anonymity may not offer protection to prevent the source of libellous comments being discovered. ISPs and bulletin board administrators can be asked to disclose the identity of the perpetrators without breaching the Data Protection Act. Even if they won't disclose these details voluntarily, they can be forced by court order when the comments posted are clearly malicious or damaging.

There can also be serious consequences for those posting fake web reviews, the seemingly innocent enough end of the business. New laws (under the Unfair Commercial Practices Directive) coming into force in the UK in April make it illegal for businesses to falsely represent themselves to consumers. It might look like “word of mouth” marketing, but is actually a lawsuit waiting to happen.

Published in The Guardian, 14 January 2008