With 32 million of us regularly using social networking sites, the blogosphere presents a tantalising marketing opportunity for the supermarkets to big themselves up - and do down their rivals. But, Simon Creasey says, it's all too easy to get your fingers burnt

Simon Uwins is no doubt still ruing the day he decided to post a progress report on his company blog. In the post last March, the chief marketing officer of Tesco's US arm Fresh & Easy revealed that the retail giant was halting the rollout of new stores in the States in order to "make improvements and allow the business to settle down".

It was the sort of juicy information that you would expect to have seen neatly packaged in a press release not slapped up on an informal blog and it was swiftly seized upon, first by the blogosphere and then by the media, triggering a massive share sale and temporarily slashing about £900m from Tesco's market value.

Uwins and Tesco learned the hard way that blogs and social media networks such as Twitter, Facebook, YouTube and Bebo, are double-edged swords. On the one hand, they are powerful communications tools with extraordinary reach: in one week alone, 9,111 discussions relating to supermarkets took place on Twitter, according to the latest data (see far right). On the other, their scale makes them difficult to police and, as Tesco discovered, it's not just attacks from disgruntled former employees or interest groups that businesses need to watch out for in the blogosphere.

So what are the rules of engagement? And what dirty tricks are retailers deploying as they try to master the dark art?

One of the biggest problems when trying to navigate the blogosphere is that the rules, such that they are, are complicated. As a result, retailers' strategies lack coherence and tend to be overly reactive, says Phil Reed, director at marketing agency Brahm. "Retailers may be monitoring, but they don't seem to be managing their brands online," he observes. "Food retailers are fortunate in that they don't attract the same level of negative coverage online as some other brands, but that's no excuse not to manage their online presence."

Perhaps having learnt a lesson from Uwins' faux pas, Tesco is one of the more proficient users of social media. It is particularly adept at defending itself from attacks, according to David Phillips, part-time digital consultant at communications agency Publicasity and author of a new book entitled Online Public Relations. "Its website has an answer for everything. It gets its defence in first before anyone attacks it. Wal-Mart hasn't, and has to spend a lot of its time defending itself."

Defence is just one side of the coin, however. Where businesses can get themselves into real trouble is when they go on the attack especially if they do it by masquerading as members of the public to whip up negative press about a rival. Whole Foods Market chief executive John Mackey was caught out doing just that when he used a pseudonym to post criticisms of then rival company Wild Oats on a financial forum, prior to acquiring the business in 2007.

And, while Wal-Mart wasn't on the attack, the retailer got into hot water in 2006 when it emerged that a blog chronicling the tales of a duo camping in WalMart car parks throughout America had actually been penned by the company's PR firm Edelman.

And when senior management or PR agencies aren't putting their foot in it, unruly members of staff are. Tesco employees famously set up a Facebook group called 'Tesco employees could rule the world', in which they called the chain's customers pestering, smelly and cheap.

"Sadly for some of the larger companies, the biggest threats are internal," says Nancy Williams, managing director of social media marketing and online reputation management company, Tiger Two. "It's not malicious stuff, but staff just don't understand how to use these things and there needs to be a process of education."

This will allow brands and their staff to control their own interaction with social media, but brands need to recognise and accept that they won't be able to control what others say about them which is where monitoring comes in. To manage a brand's reputation online you need to monitor chatter, says Reed. "You have to know what is being said about you, where it's being said and who's saying it."

This is something that can be achieved relatively cheaply and easily internally, thanks to Yahoo, Pipes, Google and Boardreader. There are also a growing number of sophisticated paid-for software options that provide more in-depth analysis. Whatever tools are used, monitoring online chatter is a great way of alerting a business to potential problems, believes Daljit Bhurji, managing director of social media consultancy Diffusion PR. "People might be complaining about a particular product, or you might notice a lot of complaints coming from a particular area, or perhaps there are lots of negative comments about a particular store."

Of course monitoring is only half the battle. A negative post needs an appropriate response. Reed suggests the following guidelines: be prompt; consider responding offline; if it's factually incorrect, correct it quickly; and always be courteous. "You'd be surprised how many aren't and it will always come back to haunt you," he says.

US retailer Target knows this all too well. Its response to a female blogger who complained about one of the company's advertisements was a terse "we are unable to respond to your inquiry because Target does not participate with non-traditional media outlets" and ended up in the news pages of the New York Times.

Response to criticism should also take into account the forum on which the comment was made. "If it's on a blog no one reads and appears far down on a search index then does it really matter?" says Ged Carroll, director of digital at PR company Ruder Finn. "However, if it's on a blog that's part of a community that's likely to get socialised, that's more important because it can spread."

If the criticism is of the latter type, it's crucial to handle the situation with full transparency. "If you control the problem in a public space on the blog where the original complaint was posted you can create an advocate out of the person who posted the blog, as well as other people who visit the site," explains Williams.

If all else fails, stealth can be used. Search engine rankings are created based on the number of links to a story, explains Giles Palmer, managing director of social media monitoring company Brandwatch, so by creating a response to negative blogs on your own website and linking to it you can drown out the original post.

Tactics like this will inevitably be rolled out more often as companies continue to fall foul of social media. The next few years will be a steep learning curve for many brand makers as they come to terms with the fact that online, they don't own the brand consumers do. By engaging with online communities instead of trying to control them, they can both manage their brand and enhance their reputation in the eyes of millions of potential customers.