BBC.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.
They don't make any money, and their costs are increasing along with their popularity. How long until they collapse, it doesn't seem at all sustainable?