.

The idea: If you find blogs self-indulgent, you’re going to hate Twitter . It’s a free online service that’s a cross between MySpace and a blog, but works on your mobile. The theme is “What are you doing?” Look at the homepage, and you’ll see thousands of people from all over the world answering the question with things such as “Just gonna cycle to the shops to buy wine” (Swanlike, Cambridge), or “Getting ready to go to new playwriting class” (imtboo, Seattle). Does this sound pointless? Hush. It’s the next big thing.

Backstory: It’s been running for a year, but exploded in March when every blogger in the world started talking about it. Subscriptions are doubling every month – there are well over 100,000 – and the owners are praying that a YouTube-style billion-dollar takeover is imminent.

How it works: You sign up for free, then connect to friends online, so they can read your “twitters”. These are mini blog posts, in fewer than 140 characters, which can be sent or received by text or through the site.

Who’s on it? At the moment, the 100 most popular Twitter users are techies twittering about Twitter, bandwagon-jumping politicians (US presidential hopeful John Edwards is “Enjoying the weekend with family”), and fictional characters - the funniest of which (by a long margin) is Darth Vader: "I told Ozzle to prepare TIE Fighters for departure & he thought I meant "thai fighters". Now my elite troopers are covered in spicy noodles"

What are they talking about? A site called Twitterverse ranks the keywords people use in messages: 1: “Twitter”; 2: “Going”; 3: “Lunch”.

Where are they? The most interesting twitter offshoot is Twittervision, a world map which shows twitters as they happen, live.

What is it for? It lets you stay in touch with friends. It might be nice to know what your mates are doing without having to call them, while for casual friends, it’s a way to meet. But once you get charged for 30 text messages a day from acquaintances wondering which sandwich to buy for lunch, the novelty might wear thin. Twitter evangelists are desperate to find ways that it's useful, claiming it could have prevented the Virginia Tech massacre, can warn about earthquakes and could replace blogging in Africa. Because what Africa needs now is... more blogs.

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