Oriental Trading Company, a US catalogue and internet retailer, sells a quirky, inflatable plastic solar system set for $17.99. The blow-up planets that hang from the ceiling are educational and engaging, but at the end of last year customers buying them from Oriental were not happy. They complained in reviews on the company's website that the sun, the eight planets and Pluto would often just not stay inflated. “I opened the package, blew up the planets, hung them in my classroom, and came in the next day to find three blobs of rubber hanging from the ceiling,” wrote one schoolteacher: “Totally disappointed!!!!”

With customers regularly giving the product low scores on its site, OTC contacted the manufacturer. By January its customer service team was able to announce it had worked with the makers to make sure the planets stayed inflated.

Its experience illustrates the evolution of a feature that has become familiar in online transactions: originally an aid to other potential buyers, online reviews are becoming a valued source of direct customer feedback for retailers and manufacturers.

Samsung Electronics started hosting online reviews on its US website last year, using technology and processing provided by Bazaarvoice, which has become the dominant provider of third-party review services in the US since it started in 2005 in a single office in Austin, Texas.

Bazaarvoice now works with more than 500 brands belonging to companies including Wal-Mart, Home Depot, Boots, Argos, Lego and Procter & Gamble. It has 400 employees providing services in 25 languages, and offices in London, Paris and Singapore, says Brett Hurt, co-founder and chief executive.

At Samsung, “it has changed some aspects of the way we work, primarily because of the speed with which information comes in,” says Kris Narayanan, Samsung's director of marketing.

The company has been using reviews in this way for less than a year, but Mr Narayanan says Samsung has already changed products in response to the new kind of feedback. For instance, large flat-panel TV sets were initially produced with speakers on the side. When customers pointed out in reviews that the units were too wide to fit into conventional cabinets, Samsung put the speakers below the screen.

“It was certainly the product reviews that clinched the issue,” Mr Narayanan says.

Sears Holdings, which owns retailers Kmart and Sears, says it is increasingly passing on information from its online reviews and discussion boards to suppliers, says Rob Harles, head of Sears's online community activities.

For Samsung, reviews are just one of several sources of consumer input it monitors, including specialised discussion boards on consumer electronics websites such as CNet, as well as the less structured discussions on social media sites such as Facebook, MySpace and Twitter.

With so much opinion to keep an eye on, the company tries to focus on analysing “qualified” input – that is, opinions from customers whoknow what they are talking about.

Sam Decker, chief marketing officer at Bazaarvoice, says such “social commerce”, as he calls it, has ballooned because it is more measurable than less focused input from open social sites.

Internet shoppers are increasingly turning to reviews on websites. Nielsen, the marketing research group, says its twice-yearly survey of more than 25,000 online consumers around the world found in April that 70 per cent trusted product reviews posted online, an increase of 9 percentage points on April 2007.