This morning’s Observer column.

One of the most intriguing and useful features in Twitter is the "retweet" facility. If you see something in your tweetstream that you think might interest others, then you can click a button to make it visible to the people who are following you. Retweeting has become so commonplace that its conventions have already been the subject of a serious study by the anthropologist Danah Boyd and her colleagues at Microsoft Research. But it turns out that retweeting is not just interesting in terms of discourse analysis; it's also the key to understanding why Twitter is a radically different form of social networking.

We know this because of a remarkable study conducted by some researchers at the Korea Advanced Institute of Science and Technology and published last week at a major academic conference…