Just as Amazon revolutionized the way books are sold and Groupon has conditioned shoppers to expect daily deals on services and foods, a cluster of websites have upended the stodgy world of wine.

At least a half-dozen online websites in the United States, a few in Britain and Australia and one or two in France promote wines, sometimes for as much as 60 percent less than retail, using social media.

But are they really good deals?

I suspect these may be OK and may be occasionally even a very good deal for the casual drinker, said Bill Marsano, a former wine editor of United Airlines magazine Hemispheres.

Fussy people, those who think highly of their wine knowledge, who prattle about terroir, will probably be disappointed. Although, a few will wake up to the fact that until they realized they like cheap wine, they were just snobs, he said.

Slurp.co.uk is an online retailer which its chief executive Dr. Jeremy Howard said operates like Amazon from a central logistics hub in London.

Like some of its U.S. counterparts it holds so-called flash sales where wines are sold at deep discounts for very short periods, sometimes as short as 30 minutes. There is a sister site in Hong Kong and both promote flash sales via Twitter and Facebook but shun email.

A study by the French management school BEM found more than a dozen websites in France, Germany and Spain, but only a few used social media. Most lacked a Facebook page and only one had a Twitter account.

By contrast, the U.S. websites use Facebook, Twitter and emails to lure customers. They differentiate themselves by offering the sales for various lengths of time, free or low-cost shipping and even storage.

Online wine sales, garnered an estimated $4 billion in sales in 2011, according to BEM, which is forecasting that number to grow to $6.5 billion in 2012.

Wine.com, WTSO.com (WTSO), Invino.com, Vitius.com as well as others, rely on Twitter, Facebook and emails to get the word out about their products.

We're not necessarily for certain, highly sophisticated customers ... We want to make wine approachable and simple for our customers, said Elliot Arking, who along with his brother Joseph and son Jamie, run WTSO.com, which stands for Wine Til Sold Out.

The daily offerings - one wine at a time - last until each wine is sold out.

Invino.com's flash sales usually last several days unlike WTSO, which generally last no more than a few hours.

Vitius.com, started by two women who each hold the title of Master of Wine, have three deals a day on average and differ from the competition primarily by offering to store customers' wines.

Wine.com is like a warehouse store that people can visit. We're just online, Rich Bergsund said. What Zappos did for shoes, we're doing for wine.

Conductor Pierre Vallet, who made his Metropolitan Opera debut last month, and lives in New York prefers to buy wine online.

It's the convenience factor and the chance to get a good deal, he said.

(Reporting By Leslie Gevirtz; editing by Patricia Reaney; For the latest Reuters lifestyle news see: http://www.reuters.com/news/lifestyle)

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