By Robert Plummer
BBC News business reporter
For the average business trying to protect and enhance its reputation, the prospect of having its actions scrutinised by an army of online commentators can feel like a threat.
Dell's image took a pounding from angry bloggers
After all, the last thing a firm wants, after spending years burnishing its corporate image, is to have its work undermined by critical accounts circulating on the internet.
But in recent years, companies ranging from UK supermarkets Tesco and Sainsbury's to worldwide computer retailer Dell have felt the wrath of dissatisfied bloggers.
Thanks to the web, people who have bad experiences with customer service departments can take their grievances to a mass audience online, with potentially serious consequences for the companies concerned.
Small wonder, then, that more and more firms are paying greater attention to what blogs are saying about them - and even trying to meet the bloggers halfway.
"Companies have been used to a level of control, and it's been very much a one-way street," says Matthew Yeomans of Custom Communication, an agency which seeks to help businesses navigate their way around the burgeoning blogosphere.
"For years, they've shut out their audience and hidden behind the world of PR. That's all blown out of the water now. They can't do that any more."
One company that found out the hard way about the power of bloggers is Dell. Last year, angry customer Jeff Jarvis detailed his frustrations with his malfunctioning Dell laptop - and his complaints about the firm's customer support - on his blog, Buzzmachine.
His postings attracted hundreds of responses and inspired comments by other bloggers.
Ultimately, the whole affair influenced public perceptions of Dell to such an extent that market researchers concluded the firm had "sustained long-term damage to its brand image".
A joint report by three firms - Market Sentinel, Onalytica and Immediate Future PR - said: "Bloggers used Jeff Jarvis' shorthand 'Dell Hell' to collaboratively spread negative comment about Dell's customer service - weakening Dell's reputation where the company used to be so strong."
Dell responded to the controversy by admitting that "Mr Jarvis' experience could've been handled better" and saying that it had begun monitoring blogs, with a view to contacting dissatisfied consumers directly.
Sainsbury's is subject to lively online discussions
Other companies facing flak from disgruntled bloggers include Britain's supermarkets, which are expected to undergo an official investigation later this year because of their dominance of the UK grocery market.
One site, supermarket-sweep-up.com, is entirely devoted to attacks on Tesco, which now accounts for more than 30% of supermarket sales in Britain.
Another blog - 173 Drury Lane - focuses on the country's number three supermarket, Sainsbury's, but tries to offer constructive criticism and "explore how Sainsbury's can create a smarter conversation with its customers and other stakeholders".
This contains opinions on Sainsbury's wine range, exhortations to do more for organic farming and even comments about the supermarket's image and marketing techniques.
It is this kind of blog that can be enormously helpful to companies if they approach it in the right way, Matthew Yeomans says.
"It can be an amazing piece of market research that you can get for free," he says.
"The more enlightened companies are not trying to control this conversation, because they realise they can't. The web is out there for anyone to see. But the best companies are seeing that as an opportunity, not a threat."
Even tailors in London's Savile Row can benefit from blogs
As part of Custom Communication, his task is to help companies keep track of what blogs have to say about them - and to help those companies "enter into that conversation" by building their own blogs.
To that end, the firm recently staged a one-day conference in London, Blogging4Business, which featured a wide range of participants.
As well as attracting representatives of big multinationals seeking a stronger relationship with their customers, the event offered plenty of evidence that even the smallest of firms can achieve a big impact by creating its own blog.
Take blogger-turned-consultant Hugh Macleod, who got involved in the medium when he set up the Gaping Void website in 2001 to showcase his work as a cartoonist.
"I was unemployed and I started exploring blogs - I was scraping a living as a freelance," he says.
"One of my drinking buddies was a Savile Row tailor, Thomas Mahon, and I said to him, 'You should start a blog.' So we created English Cut, the first tailoring blog.
"To cut a long story short, if you search Google for 'Savile Row', we're number one. His tailoring business thrived in a very short space of time."
Mr Macleod then moved on to work for a small South African wine company, Stormhoek, using his Gaping Void site as a vehicle for what he calls "wine blogging as marketing disruption".
In the first phase, he sent out free bottles of wine to about 100 bloggers in the UK, Irish Republic and France. Only those who had regularly kept up a blog for at least three months could apply, but the size of their readership didn't matter - "just so long as they were genuine bloggers".
As a result, a lot of those bloggers ended up writing about Stormhoek wine. In the wake of his campaign, sales doubled, rising from 50,000 cases in 2004 to 100,000 last year.
In the next phase of the campaign, Stormhoek has started sponsoring "geek dinners", offering to provide free wine for bloggers' dinner parties.
As part of its forthcoming launch in the US, the firm wants to have "100 geek dinners in 100 days", running from 1 May to 9 August.
From the vine to the table of the discerning geek...
"What I'm interested in is what I call the global micro-brand," says Mr Macleod.
"Now with the internet, creating global micro-brands is cheaper and easier than ever before. You can start off and have a product and market it on a global level much more easily than even 10 years ago."
Mr Macleod points out that blogging can be hard work: "The blogs don't write themselves, and it takes a while for the voice to emerge - you have to hone it to where you want it to be.
"It's all virgin snow and we're still dealing in unknown quantities, but that's what makes it exciting.
"The number of new blogs is not going down and people are still paying attention to them. Something's working and it's not obvious what that is."