Twitter is being used as a broadcast medium, the study says
Micro-blogging service Twitter remains the preserve of a few, despite the hype surrounding it, according to research.
Just 10% of Twitter users generate more than 90% of the content, a Harvard study of 300,000 users found.
Estimates suggest it now has more than 10 million users and is growing faster than any other social network.
However, the Harvard team found that more than half of all people using Twitter updated their page less than once every 74 days.
And most people only ever "tweet" once during their lifetime, the researchers found.
"Based on the numbers, Twitter is certainly not a service where everyone who has seen it has instantly loved it," said Bill Heil, a graduate from Harvard Business School who carried out the work.
On a typical online social network, he said, the top 10% of users accounted for 30% of all production.
"This implies that Twitter's resembles more of a one-way, one-to-many publishing service more than a two-way, peer-to-peer communication network," the team wrote in a blog post.
Twitter is a social networking website where people can post messages of up to 140 characters - known as tweets - that can be seen by other users who subscribe to their feed.
Its growth has been described as "explosive" and it has become the poster child of social networking sites, particularly among media companies.
Recent figures from research firm Nielsen Online show that visitors to the site increased by 1,382%, from 475,000 to seven million, between February 2008 and February 2009. It is thought to have grown beyond 10 million in the past 4 months.
By comparison, Facebook - one of the most popular social networking sites by number of visitors - has 200 million active users and grew by 228% during the same period.
Research by Nielsen also suggests that many people give the service a try, but rarely or never return.
Earlier this year, the firm found that more than 60% of US Twitter users failed to return the following month.
"The Harvard data says very, very few people tweet and the Nielsen data says very, very few people listen consistently," Mr Heil told BBC News.
The Harvard study took a snapshot of 300,542 users in May 2009. As well as usage patterns it looked in detail at gender differences.
For example, it found that men had 15% more followers than women despite there being slightly more females users of Twitter than males.
It also showed that an average man was almost twice as likely to follow another man than a woman, despite the reverse being true on other social networks.
"The sort of content that drives men to look at women on other social networks does not exist on Twitter," said Mr Heil.
"By that I mean pictures, extended articles and biographical information."
However, said Mr Heil, the most striking result was that so few people used the service to publish information, preferring instead to be passive consumers.
For example, the median number of lifetime tweets per user is one.
"Twitter is a broadcast medium rather than an intimate conversation with friends," he said.
"It looks like a few people are creating content for a few people to read and share."
Some "super users" can have thousands or even hundreds of thousands of followers.
Currently, the most popular person to follow on Twitter is the movie star Ashton Kutcher who has more than two million followers.
However, the service bills itself as a way to "communicate and stay connected" with "friends, family and co-workers".
"The Twitter management need to decide if this is a problem," said Mr Heil.
"And if they decide it is, how they will tweak Twitter to become more acceptable to the average user?"
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