I've never seen anything take off as quickly as Twitter appears to have done in the last couple of weeks. It seems a classic case of the way that ideas now spread. They travel through circles of friends. You join because you know a few friends who have joined it already. If you didn't know anyone who had tried it nothing else would ever possess you to give it a go. Here's mine.
I've come round to the view that people are now drawn to many things - books, bands, magazines, particularly magazines - through friends. In that sense propagating a magazine today is less a question of introducing the magazine to new readers than was formerly the case. Instead it's like expanding your circle of friends. You do it through baby steps and close encounters rather than by giant strides and big gestures.
I also wonder if the current financial situation has provided Twitter with the perfect moment. Right now people want to hold hands, even if it's via a screen. It costs nothing. And for those who are coping with unemployment it's the perfect way to say "I'm still here."