According to stats compiled by eMarketer, comScore reported that Twitter.com drew 4 million unique visitors from home, work and college/university locations in February 2009, up from 340,000 a year earlier -- a 1,086% increase. Nielsen Online reported 7 million unique visitors to Twitter.com during March 2009, up even higher -- 1,381% -- from 475,000 the prior year.
eMarketer projects that the number of Twitter users will jump to 18.1 million in 2010, representing 10.8% of Internet users.
What is driving this meteoric adoption?
Well, clearly the appearance of Twitter's CEO on The Oprah Winfrey Show didn't hurt. But what's the long-term value to users?
A survey of Twitter users from MarketingProfs referenced by eMarketer reports that, on a scale from 1 to 5 (with 1 for strongly disagree and 5 and for strongly agree), the phrase “I find it exciting to learn new things from people” averaged a score of 4.65 and “I value getting information in a timely manner” averaged 4.58. In short, Twitter users are motivated by the opportunity for real-time information.
I guess think of Twitter as public instant messaging. For those of us who have been instant messaging with friends and colleagues privately on Skype and other services for several years, the value was always instant communication on real-time issues (e.g., "can we meet up in an hour at the Starbucks on 57th Street?").
Twitter brings the value of "instant messaging" to the public sphere. While private messages obviously need to remain private, Twitter facilitates the instant dissemination of messages of immediate relevance to the "public" (which can be defined either broadly such as the general public, or narrowly such as a close circle of friends or peers).
See the full eMarketer article referenced above here.