While big Twitter fans are spending more time on on the site, many US users are abandoning it or using it increasingly rarely.
A study from Experian Simmons has found that the number of US adults paying a monthly visit to microblogging site Twitter.com has fallen during the past year by 14 percent.
During November, 8.25 million people made at least one visit to Twitter.com, down from 9.54 million in the previous month.
And when people do use the site, they're spending less time there, suggesting visitors are now seeking more frequent quick hits, rather than spending longer periods of time reading through posts.
According to Experian, the average amount of time Twitter.com visitors spend on the site during a typical session fell to 13 minutes, 12 seconds on November 27, 2010, down from an average of 15 minutes, 12 seconds on November 28, 2009.
"Does this mean the ultimate 'fail whale' is lurking just over the horizon for Twitter?" asks the firm - and concludes that it isn't.
For those who do visit Twitter.com, it says, the average number of visits per month rose by over a third in the last year, hitting an average of 10.0 visits in November, up from just 7.3 visits in the same month a year earlier.
And this means Americans are still spending more time on Twitter.com than ever before. Experian estimates that Americans spent two hours and 12 minutes tweeting and reading tweets on Twitter.com in November 2010, up from one hour and 51 minutes spent on the site during November 2009.