Showing off
Exhibitionism
Most people feel tiny, anonymous and insignificant or at the very least fear becoming so. The Internet potentially gives you access to the attention of the whole world and every bit of attention you get goes some way towards affirming your importance, your relevance, your very existence.
In this sense it is just another Web 2.0 tool alongside sites like Facebook and Myspace as well as countless forums, chatrooms and blogs.
The Times yesterday gathered some shrinks and all purpose experts with the apparent intention of proving this. "Twittering stems from a lack of identity," said one, "We are the most narcissistic age ever," concurred another. Alain de Botton reckons it's a way of proving you're alive, concluding witheringly: "It is a giant baby monitor."
"It is a giant baby monitor"
Celebrities
You could argue this is an extension of the above. Celebrities are defined by their popularity and Twitter is another way of ensuring popularity by connecting with their fans and maybe acquiring new ones. It doesn't seem to have done Stephen Fry any harm.
Voyeurs
You don't have to write a single tweet to participate in Twitter, you can just subscribe to a bunch of other people and see what they've got to say. In the case of celebrities this can be especially appealing as it creates the, usually mistaken, sensation of having a personal dialogue with said celeb.