Britney Spears, Ashton Kutcher, and John Mayer are among the many celebs who have adopted micro-blogging

By Adam Markovitz
Updated March 06, 2009 at 05:00 AM EST

Last Friday, Britney Spears packed up for a trip home to Louisiana. A few hours later, Ashton Kutcher watched 27 Dresses, Ryan Seacrest oversaw renovations at his radio studio in L.A., and Lily Allen cooed over a bouquet of pink flowers sent by her record label. The following day, John Mayer pooped.

No, these aren’t reports from a squad of celeb stalkers. All this information was broadcast — for better or worse — by the stars themselves via Twitter, a free online venture that lets anyone with a computer, cell phone, or mobile device live-blog their thoughts to the world in 140-character bites. The three-year-old site is growing fast — posting a 900 percent increase in active users since last year — and getting name-checked by Doonesbury, The Daily Show, and even the Web-challenged ladies of The View (and all that was on March 2 alone).

All this buzz begs the question: Will Twitter be the next Facebook or another Friendster-style fizzle? While the company doesn’t release user data, Twitter’s most popular user, President Barack Obama, has 339,500 followers on the site — a fraction of his 5,767,400 supporters on Facebook (he hasn’t posted since Jan. 19). Still, Internet gurus say the site may be here to stay. ”Are they going to get as big as Yahoo! and Microsoft? Probably not,” says Alex Patriquin, a senior analyst at Web-analytics firm Compete. ”But are they a flash in the pan? Absolutely not. They’re already too established.”

The basic Twitter experience starts with logging on — either via or one of the thousands of third-party applications that interface with it — and choosing the people whose posts (or ”tweets”) you’d like to receive. As those people respond to Twitter’s ever-present prompt — ”What are you doing?” — their answers pile up on your homepage in a time-stamped list resembling a short-attention-span blog.

More and more stars are trying their hand at tweeting, which is clearly a growing part of the site’s appeal. You’ll find singer Taylor Swift plugging her new video, comic John Cleese chatting with fans about pet peeves, and The Office‘s Rainn Wilson riffing on TV: ”America’s Funniest Home Videos should be re-named ‘Americans love hideous trampoline accidents.”’ Says Twitter cofounder Evan Williams: ”We didn’t anticipate the celebrities, but fans love it. They get an authentic view into these people’s real lives.”

And stars are obviously enjoying it too. ”I was fascinated by the immediacy and the power of Twitter,” says author Neil Gaiman (Coraline). ”I love the idea of unmediated interactions.” Singer Sara Bareilles, who joined on the advice of her label, adds, ”It’s a way to keep fans feeling connected to who you are, but I won’t post about what I had for lunch.”

That direct line of communication to fans also makes Twitter a potential windfall for viral marketing. Jimmy Fallon drummed up publicity for his new Late Night stint with near-hourly updates on the day of his debut, and producers of Showtime’s Californication set up an account for the show’s wannabe-writer character Mia Cross (Madeline Zima).

But not all that Twitters is gold. Stars like Tina Fey and Emma Watson (who plays Hermione in the Harry Potter films) have recently debunked bogus accounts created by overzealous fans. And many celeb posts are either purely promotional (ahem, Anderson Cooper) or simply boring (see sidebar).

Twitter’s founders haven’t yet announced how they will cash in on the site’s popularity — let alone figured out how to measure it. ”It’s actually really hard even for us to estimate total traffic,” says Williams. The exec confirms that Facebook was in talks to buy Twitter last October. The reported $500 million deal fell apart, but Williams says the companies are still in touch. Probably by phone.