By last December, 11% of Web-equipped U.S. adults said they used such a service to put out updates about themselves or follow the updates of others, according to a report released Thursday by the Pew Internet & American Life Project.

Pew's findings are based on data from telephone interviews with 2,253 U.S. adults conducted late last year by Princeton Survey Research Associates International.

Perhaps demonstrating the rapid rise in short-message sharing services, just a few weeks earlier, in November of last year, 9% of Web users reported using a Twitter-like service, while in May of last year, 6% reported using the service.

What's more, Twitter--which Pew deems "the most well-known" such service--has only been around since August 2006.

For the uninitiated, Twitter allows users--referred to as "Twits"--to send messages, known as "Tweets" from a computer or a mobile device like a mobile phone, BlackBerry or iPhone. Users of the service are asked to post messages of 140 characters and those messages are delivered to others who have signed up to receive them such as family, friends or colleagues.

"The use of Twitter is highly intertwined with the use of other social media," according to Amanda Lenhart, senior research specialist at Pew. "Both blogging and social network use increase the likelihood that an individual also uses Twitter."

Indeed, nearly one quarter--23%--of social network users say they have used Twitter or a similar service. In comparison, just 4% of those who do not use social networks have ever tweeted.

Meanwhile, 27% of bloggers use Twitter, compared with just 10% of those who do not keep a blog. Overall, 13% of Internet users have created a blog.

Twitter's open development platform allows outside developers to build add-on applications to expand the service's functionality. Twits can select from a variety of third-party Twitter interfaces, browser plug-ins, photo- and video-sharing applications.

For many Twits, learning about and sharing relevant and recent nuggets of information is a primary utility of the service, according to Pew.

While Twits are just as likely as others to consume news on any given day, they are more likely to consume it on mobile devices and less likely to engage with news via more traditional outlets. Twits are less likely to read a printed copy of a newspaper, but more likely to read a newspaper online--76% vs. 60% of non-Twits--and more likely to read a news story on a cell phone--14% vs. 6%--or on a smart phone--7% vs. 7%.

Not surprisingly, Twitter and similar services have been most avidly embraced by young adults. Nearly one in five--19%--of online adults ages 18 and 24 have used Twitter and rival services, as have 20% of online adults ages 25-34.

Use of these services drops off steadily after age 35 with 10% of 35- to- 44-year-olds and 5% of 45- to-54-year-olds using Twitter. The decline is even more stark among older Internet users; 4% of 55- to 64-year-olds and 2% of those ages 65 and older use Twitter.

As a result, online Americans who live in lower-income households are more likely to use Twitter than more affluent Americans , Pew found. Some 17% of internet users in households earning less than $30,000 tweet and update their status, compared with 10% of those earning more than $75,000 annually.

However, Twitter use is not dominated by the youngest of young adults, as the median age of a Twitter user is 31. By comparison, the median age of a MySpace user is 27, while Facebook users median at 26 and LinkedIn users at 40.

Also, Twits are slightly more racially and ethnically diverse than is the full U.S. population, most likely because they are younger--and younger Americans are a more ethnically and racially diverse group than is the full population, according to Pew.

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