The fragmented nature of the market for fine wines typically involves multiple middlemen - each levying his own healthy mark-up - and asymmetrical data, as vendors always had better information on pricing than the buyers. But like the wines they sell, the industry is slowly maturing.

Those who still use the web as a tool would be well advised to check their prices against information on several websites that track wine prices among specialised traders, adding transparency and flattening margins.

One of those websites is Liv-Ex. It's a trading platform that is used by 440 industry members who place bids and offer orders on the site 24 hours a day. Their data is widely used in the industry.

The firm makes money though trading fees and selling data. One of the founders is Justin Gibbs. A former London stockbroker, Gibbs and long-time friend and Liv-ex co-founder James Miles were used to thin margins and centralised clearing houses - the antithesis of the late 1990s wine market.

By opening transaction data to public scrutiny, the firm helped to both increase buyer interest and grow the overall market.

"Every time you bring transparency to a marketplace, you bring with it standardisation and confidence," Gibbs said.

Since Liv-ex began, Gibbs estimates that British wine merchant margins have dropped from 20 to 25 per cent to 10 to 15 per cent. Over the same period, global sales for fine wine quadrupled to US$4 billion.

According to Gibbs, Liv-ex transactions totalled £102 million (HK$1.3 billion) in 2011 and £87 million in 2012.

Price transparency was not universally welcomed. Some merchants were "a little bit grumpy" when Liv-ex and Wine-Searcher arrived, says Jonathan Reeve, content manager at Wine-Searcher, which is based in New Zealand.

"But you can't really get away with charging very high prices and hoping your customers won't know the wine isn't worth that," said Reeve.

The website started in 1999. It uses "spider" software that trawls the web for wine prices, and collates this information into one searchable database. The site also shows average and historical price data so traders have reference points when negotiating.

In late February, the site had 5.86 million live offers from 42,700 wine merchants around the globe.

This transparency is making an impact on prices. In a study last year the firm traced the price trends of more than 200,000 wines sold in the US over the past decade. In 2003, one in five merchants listed their wines at 40 per cent above the average price. Last year, only 2 per cent of merchants priced their wines at the same premium.

Another firm is iDealwine. The Paris-based fine wine online auction firm recently opened an office in Hong Kong. It has two auctions a month and targets mid- to high-end buyers with an average per-bottle price of HK$740.

"Online is really for people who know wine," said Claire Henry, the firm's Asia relations manager. "People coming through our website are looking for something special, something they cannot find in a [shop]."

The site has 350,000 members worldwide and had sales of HK$116 million in 2012.

Some functions on these sites have drawn criticism. "Anyone can go out there and undercut your price list, but whether they can actually supply the wine is a different issue," Jo Purcell said about Wine-Searcher. "It's not 100 per cent accurate." Purcell is Hong Kong managing director at Farr Vintners, one of Britain's largest wholesale wine traders.

Fake listings come about when merchants dangle keenly priced wines on their websites to draw hits and e-mail traffic. The wine does not exist, but the potential buyer may be persuaded to take something else once an e-mail exchange with the wine merchant begins - a classic bait and switch.

Wine-Searcher sells data. If a buyer likes a price, he clicks through to the merchant directly. The site does not vet the firms it lists, but it will investigate complaints about fake listings. Reeve said the website delists five to 10 firms a year based on such complaints.

Purcell said established professional vendors provide valuable services - specifically, verification, cataloguing and storage of wines ahead of a sale - that command a price. She said a 10 per cent mark-up is a fair premium over the pure market price. Below that, the business loses money.

Many customers like dealing with established merchants because such vendors have reputations to protect and are accountable for the authenticity and quality of the goods they sell.

"The big problem comes back to provenance and whether you know who you are dealing with," said Purcell. "How do you know that person listing bought the stock from a reliable seller and whether it's a reliable stock and has been stored properly all its life?"

Platforms approach this issue in different ways. Liv-ex acts as a clearing house, but the firm has only a relatively small number of listed traders who are all known entities in the wine business. Gibbs said the firm established a committee to oversee disputes with the threat of expulsion for non-compliance.

The staff of iDealwine source wines only from Europe, and they perform visual inspections on new arrivals to check for defects and fakes, Henry said.

BBX, Berry Bros & Rudd's online platform, restricts trading to bottles held by its customers and stored in the firm's warehouses outside London. This limits the stock range, but the firm can then offer assurances on provenance. Berry Bros & Rudd has 30,000 customers holding £600 million in wine.

"We had so many customers with so much wine, we couldn't really represent it as well as we possible could," said Simon Staples, sales director at Berry Bros & Rudd, on why the firm launched BBX in August 2010. From then to January this year, £50 million of wine traded on BBX, and the site now attracts 250,000 to 300,000 unique visitors each month.

Mirfin, the Hong Kong auditor, would like to see other merchants start their own versions of BBX. It would be another step towards increased liquidity and turnover. However, the challenge of settlement remains.

In Britain, the wine storage market is dominated by two firms, Octavian Vaults and London City Bond. "What happens is, the cases just go up and down the M4 as the ownership changes," adding to transaction costs, said Gibbs, referencing the main motorway connecting London to the west of England.

Merchants say a better model would involve coding of wine cases at the vineyard and the client's ownership data to be centrally recorded or shared, effectively another step towards a local or international clearing house for wine transactions. A case then can stay put in a warehouse while buyers trade ownership certificates. But without co-ordination or leadership among vineyards, this is likely to remain a bottle dream.